Document

424B5 1 viant-prosuppx424b5.htm 424B5 Document

Filed Pursuant to Rule 424(b)(5)

Registration No. 333-278177

The information in this preliminary prospectus supplement and the accompanying prospectus, relating to an effective registration statement under the Securities Act of 1933, as amended, is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities, and neither we nor the selling stockholder is soliciting an offer to buy these securities, in any state or other jurisdiction where the offer or sale is not permitted.

Subject to completion, dated September 16, 2026

PRELIMINARY PROSPECTUS SUPPLEMENT

(To prospectus dated April 23, 2024)

8,500,000 Shares

Viant Technology Inc.

Class A Common Stock

The selling stockholder identified in this prospectus supplement (the “selling stockholder”) is offering 8,500,000 shares of our Class A common stock. We will not receive any proceeds from the sale of our Class A common stock by the selling stockholder.

We will grant the underwriters an option, exercisable for 30 days after the date of this prospectus supplement, to purchase up to an additional 1,275,000 shares of our Class A common stock from us at the public offering price, less the underwriting discount. We will receive all of the net proceeds from the sale of any shares of Class A common stock sold by us upon exercise of that option.

Our Class A common stock is listed on the Nasdaq Global Select Market (“Nasdaq”) under the symbol “DSP.” The last reported sale price of our Class A common stock on Nasdaq on September 15, 2026 was $12.60 per share.

We have two classes of common stock outstanding: Class A common stock and Class B common stock. Each share of Class A common stock and Class B common stock entitles its holder to one vote on all matters presented to our stockholders generally. All of our Class B common stock is held by the Continuing LLC Owners (as defined herein), on a one-for-one basis with the number of Class B units they own.

We are a holding company and our sole material asset is a controlling equity interest in Viant Technology LLC and Class B units we acquire directly from the Continuing LLC Owners. As the sole managing member of Viant Technology LLC, we operate and control all of the business and affairs of Viant Technology LLC and, through Viant Technology LLC and its subsidiaries, conduct our business. As of June 30, 2026, before giving effect to this offering, we owned a 31.7% economic interest in Viant Technology LLC. The remaining 68.3% economic interest in Viant Technology LLC was owned by the Continuing LLC Owners through their ownership of Class B units. After giving effect to this offering (assuming no exercise of the underwriters’ option to purchase additional shares, as described below), we expect to own an approximately 44.5% economic interest in Viant Technology LLC. In addition, we are, and after giving effect to this offering will continue to be, a "controlled company" (as defined by Nasdaq Listing Rule 5615(c)(1)) because Tim Vanderhook, Chris Vanderhook and Capital V LLC hold, and will continue to hold, more than 50% of the voting power for the election of directors. See the “Selling Stockholder” section on page S-13 of this prospectus supplement and the risk factors incorporated by reference into this prospectus supplement.

We are an “emerging growth company” and “smaller reporting company” as defined under the federal securities laws and, as such, we have elected to comply with certain reduced reporting requirements for this prospectus supplement and may elect to do so in future filings.

Investing in our Class A common stock involves risks that are described in the “Risk Factors” section beginning on page S-9 of this prospectus supplement, the “Risk Factors” section beginning on page 7 of the accompanying prospectus, and in the documents incorporated by reference into this prospectus supplement and the accompanying prospectus.


	Per Share	Total
Public offering price	$	$
Underwriting discounts and commissions(1)	$	$
Proceeds, before expenses, to the selling stockholder(2)	$	$

____________________

(1)See “Underwriting” beginning on page S-18 of this prospectus supplement for additional information regarding underwriting compensation.

(2)Assumes no exercise of the underwriters’ option to purchase additional shares of Class A common stock from us.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares of Class A common stock against payment therefor on or about , 2026.


Evercore ISI			Wells Fargo Securities


RBC Capital Markets			Craig-Hallum

The date of this prospectus supplement is , 2026.

TABLE OF CONTENTS

Prospectus Supplement


			Page
ABOUT THIS PROSPECTUS SUPPLEMENT			S-1
BASIS OF PRESENTATION			S-2
TRADEMARKS, TRADE NAMES AND SERVICE MARKS			S-3
MARKET AND INDUSTRY DATA			S-4
PROSPECTUS SUPPLEMENT SUMMARY			S-5
THE OFFERING			S-7
RISK FACTORS			S-9
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS			S-11
USE OF PROCEEDS			S-12
SELLING STOCKHOLDER			S-13
MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS TO NON-U.S. HOLDERS OF CLASS A COMMON STOCK			S-14
UNDERWRITING			S-18
LEGAL MATTERS			S-27
EXPERTS			S-27
WHERE YOU CAN FIND MORE INFORMATION			S-27
INCORPORATION OF DOCUMENTS BY REFERENCE			S-28

Prospectus


			Page
ABOUT THIS PROSPECTUS			1
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS			2
TRADEMARKS			3
WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE			4
THE COMPANY			6
RISK FACTORS			7
USE OF PROCEEDS			8
DESCRIPTION OF CAPITAL STOCK			9
DESCRIPTION OF DEBT SECURITIES			14
DESCRIPTION OF WARRANTS			22
DESCRIPTION OF PURCHASE CONTRACTS			24
DESCRIPTION OF UNITS			25
SELLING STOCKHOLDERS			30
PLAN OF DISTRIBUTION			31
LEGAL MATTERS			33
EXPERTS			33

Neither we, the selling stockholder nor the underwriters have authorized anyone to provide any information or to make any representations other than those contained or incorporated by reference herein, in the accompanying prospectus or in any free writing prospectus prepared by us or on our behalf to which we have referred you. Neither we, the selling stockholder nor the underwriters take responsibility for, or provide any assurance as to the reliability of, any other information that others may give you. This prospectus supplement and the accompanying prospectus

do not constitute an offer to sell, or a solicitation of an offer to buy, any securities other than the shares of Class A common stock offered hereby, and do not constitute an offer to sell, or a solicitation of an offer to buy, such shares in any circumstances or jurisdiction in which such offer or solicitation is unlawful. You should assume that the information contained, or incorporated by reference, in this prospectus supplement and the accompanying prospectus is accurate only as of the date on the cover of the applicable document. Our business, financial condition, results of operations and prospects may have changed since that date.

ABOUT THIS PROSPECTUS SUPPLEMENT

On March 22, 2024, we filed with the Securities and Exchange Commission (the “SEC”) a registration statement on Form S-3 (File No. 333-278177) under the Securities Act of 1933, as amended (the “Securities Act”), which was amended on April 8, 2024, utilizing a shelf registration process relating to the securities described in this prospectus supplement. The registration statement, as amended, was declared effective by the SEC on April 23, 2024.

This document has two parts. The first part is this prospectus supplement, which describes the specific terms of an offering of our Class A common stock by us and the selling stockholder and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference into the accompanying prospectus. The second part, the accompanying prospectus, provides more general information, some of which does not apply to this offering. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. If the information in this prospectus supplement is inconsistent with the accompanying prospectus or any document incorporated by reference therein filed prior to the date of this prospectus supplement, you should rely on the information in this prospectus supplement.

It is important for you to read and consider all of the information contained in this prospectus supplement and the accompanying prospectus in making your investment decision. We include cross-references in this prospectus supplement and the accompanying prospectus to captions in these materials where you can find additional related discussions. The table of contents in this prospectus supplement provides the pages on which these captions are located. You should read both this prospectus supplement and the accompanying prospectus, together with the additional information described in the sections entitled “Where You Can Find More Information” and “Incorporation of Documents by Reference” of this prospectus supplement, before investing in our Class A common stock.

We and the selling stockholder are offering to sell, and seeking offers to buy, shares of Class A common stock only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement and the accompanying prospectus and the offering of the Class A common stock in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement and the accompanying prospectus must inform themselves about, and observe any restrictions relating to, the offering of the Class A common stock and the distribution of this prospectus supplement and the accompanying prospectus outside the United States. This prospectus supplement and the accompanying prospectus do not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement and the accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

S-1

BASIS OF PRESENTATION

As used in this prospectus supplement, unless the context otherwise requires, references to:

•“we,” “us,” “our,” the “Company,” “Viant Technology Inc.” and similar references refer (1) following the consummation of our initial public offering (the “IPO”) which occurred on February 9, 2021, to Viant Technology Inc. and, unless otherwise stated, all of its subsidiaries, including Viant Technology LLC, and (2) prior to the completion of the IPO, to Viant Technology LLC.

•“you” refers to potential investors in our Class A common stock.

•“Class A units” refers to Class A units of our subsidiary, Viant Technology LLC.

•“Class B units” refers to Class B units of our subsidiary, Viant Technology LLC.

•“Continuing LLC Owners” refers collectively to holders of Class B units and our Class B common stock after giving effect to our IPO who may exchange their Class B units for an equivalent number of shares of our Class A common stock (together with the automatic retirement of their shares of our Class B common stock on a one-for-one basis with the number of Class B units so exchanged).

•“Tax Receivable Agreement” refers to the tax receivable agreement, dated as of February 9, 2021, among Viant Technology Inc., Viant Technology LLC and the Continuing LLC Owners, as amended from time to time.

S-2

TRADEMARKS, TRADE NAMES AND SERVICE MARKS

This prospectus supplement includes, or incorporates by reference, our trademarks and trade names which are protected under applicable intellectual property laws and are our property. This prospectus supplement also contains, or incorporates by reference, trademarks, trade names and service marks of other companies, which are the property of their respective owners. Solely for convenience, trademarks, trade names and service marks referred to, or incorporated by reference, in this prospectus supplement may appear without the ®, ™ or SM symbols, but such references are not intended to indicate, in any way, that we will not assert, to the fullest extent permitted under applicable law, our rights or the right of the applicable licensor to these trademarks, trade names and service marks. We do not intend our use or display of other parties’ trademarks, trade names or service marks to imply, and such use or display should not be construed to imply, a relationship with, or endorsement or sponsorship of us by, these other parties.

S-3

MARKET AND INDUSTRY DATA

We include in this prospectus supplement statements regarding factors that have impacted our and our customers’ industries. Such statements are statements of belief and are based on industry data and forecasts that we have obtained from industry publications and surveys, including those published prior to the date on the cover of this prospectus supplement. Industry publications, surveys and forecasts generally state that the information contained therein has been obtained from sources believed to be reliable, but there can be no assurance as to the accuracy or completeness of such information. In addition, while we believe that the industry information included herein is generally reliable, such information is inherently imprecise. While we are not aware of any misstatements regarding the industry data presented herein, we have not independently verified the industry information. Our estimates involve risks and uncertainties and are subject to change based on various factors, including those discussed under the caption “Risk Factors” in this prospectus supplement, as well as the other risk factors incorporated by reference in this prospectus supplement. Accordingly, investors should not place undue reliance on this information.

S-4

PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights information contained elsewhere in this prospectus supplement or incorporated by reference into this prospectus supplement and the accompanying prospectus. This summary is not complete and does not contain all of the information that you should consider before investing in our Class A common stock. Before investing in our Class A common stock, you should carefully read this entire prospectus supplement, the accompanying prospectus, any applicable free writing prospectus prepared by us or on our behalf to which we have referred you and the information incorporated herein by reference, including the financial data and related notes and the risk factors contained in this prospectus supplement, our Annual Report on Form 10-K for the year ended December 31, 2025 (the “2025 10-K”) and our subsequent Quarterly Reports on Form 10-Q filed with the SEC. Unless the context requires otherwise, references to “our company,” “we,” “us” and “our” refer to Viant Technology Inc. and its direct and indirect subsidiaries, including Viant Technology LLC.

The Company

We are an advertising technology company. Our cloud-based demand side platform (“DSP”) enables the programmatic purchase of advertising, which is the electronification of the digital advertising buying process. Our proprietary data, measurement, AI and other technology-enabled solutions enhance advertising planning, execution and performance. Programmatic advertising is rapidly taking market share from traditional ad sales channels, which require more staffing, offer less transparency and involve higher costs to buyers.

Our DSP is used by marketers and their advertising agencies to centralize the planning, buying and measurement of their digital advertising across most channels. Through our omnichannel platform, a marketer can easily buy ads on connected TV, streaming audio, digital out-of-home, mobile and desktop.

Additionally, our artificial intelligence product suite, ViantAI, is the foundational component of our long-term vision for autonomous advertising. We expect it to power every stage of the programmatic advertising lifecycle and create the most efficient and cost-effective experience for our customers. Our ViantAI suite currently includes AI Planning, which enables media planners to design high-impact campaigns in seconds, AI Bidding, which optimizes inventory costs by lowering the effective cost per mille through automated bid adjustments, AI Measurement and Analysis, which provides accessible measurement and insights via a user-friendly chat interface, and recently released AI Decisioning, which automates planning, execution, measurement and dynamic optimization of campaigns in real-time. The launch of AI Decisioning was accompanied by the introduction of Outcomes, our autonomous advertising performance solution that utilizes each of the four phases of ViantAI, and various signals within our intelligence layer, to build and execute campaigns designed to deliver an optimal outcome.

Our DSP is an easy-to-use self-service platform that provides our customers with transparency and control over their advertising campaigns. Customers can choose to maintain hands-on control over every campaign detail or have our platform autonomously execute, optimize and measure their advertising investments. Our platform offers customers unique visibility across a variety of inventory, allowing them to create customized audience segments and leverage our proprietary data and addressability solutions, including Household ID, IRIS_ID, and attention signals, as well as strategic partner data, to reach target audiences at scale. Our platform delivers a full suite of forecasting, reporting and built-in automation that provides our customers with insights into available inventory based on the desired target audience.

We generate revenue from platform fees and fees related to the purchase of our proprietary data, measurement, and technology service offerings pursuant to agreements that enable a wide variety of marketers and their agencies to select the mix of pricing and service options that suits their unique business and advertising needs. Our platform pricing options consist of a percentage of spend pricing option and a fixed cost per mille pricing option.

We believe that offering a mix of pricing and service options provides greater flexibility for marketers and their advertising agencies seeking to plan, buy and measure programmatic campaigns using our platform and related data, measurement and technology-enabled solutions.

S-5

Our Market Opportunity

We believe that over the long term, our total addressable market is the total global advertising market, which eMarketer has forecasted as of June 12, 2026 to grow from $1.2 trillion in 2026 to $1.5 trillion in 2029, a 9% compound annual growth rate ("CAGR"). Currently, our focus is primarily on the U.S. market, which eMarketer has forecasted to grow from $485 billion in 2026 to $576 billion in 2028, a 9% CAGR, primarily including the following segments:

• CTV: U.S. CTV advertising is forecasted to be a $37.0 billion market in 2026 and forecasted to grow to a $47.6 billion market in 2028, a 13% CAGR. CTV includes over-the-top (“OTT”) content delivered through a connected device over the internet.

• Desktop and Mobile: U.S. desktop and mobile advertising are forecasted to grow from a $363 billion market in 2026 to a $450 billion market in 2028, a 11% CAGR.

• Streaming Audio: U.S. digital audio advertising is forecasted to be an $8.0 billion market in 2026 and forecasted to grow to an $8.9 billion market in 2028, a 6% CAGR.

• Digital Billboards: U.S. billboard advertising is forecasted to be a $4.9 billion market in 2026 and forecasted to grow to a $5.7 billion market in 2028, a 8% CAGR.

The forecasts for each segment above include both programmatic and non-programmatic digital advertising. In recent years, programmatic advertising has represented an increasing portion of total U.S. media spend. eMarketer estimates, as of May 5, 2026, that the U.S. programmatic advertising market, as represented by the segments above, will grow from $221 billion in 2026 to $279 billion in 2028, a 12% CAGR.

Recent Developments

On May 1, 2026, we completed our acquisition of TVision Insights, Inc. (“TVision”), adding attention measurement and data capabilities that we are integrating into our platform and broader product offerings alongside our existing measurement, data, content and identity capabilities.

Corporate Information

We were incorporated in Delaware on October 9, 2020. In connection with the consummation of our IPO in February 2021, we became the sole managing member of Viant Technology LLC. Our principal executive offices are located at 2722 Michelson Drive, Suite 100, Irvine, CA 92612, and our telephone number is (949) 861-8888. Our Class A common stock is listed on the Nasdaq Global Select Market under the symbol “DSP.” Our website address is www.viantinc.com. The information on, or accessible through, our website is not part of this prospectus supplement or the accompanying prospectus.

Evaluation of Jurisdiction of Incorporation

Our board of directors has formed a special committee consisting solely of independent directors to evaluate whether we should remain incorporated in Delaware or reincorporate in another state. As of the date of this prospectus supplement, no decision has been made by the special committee or our board of directors as to whether we should remain incorporated in Delaware or reincorporate in another state. Any such reincorporation would also require the approval of our stockholders. For so long as Tim Vanderhook, Chris Vanderhook and Capital V LLC collectively hold a significant amount of the voting power of our common stock, they would be able to control or significantly influence whether our stockholders approve any such reincorporation.

S-6

THE OFFERING


Selling stockholder						Capital V LLC.

Class A common stock offered by the selling stockholder						8,500,000 shares, which will be issued to the selling stockholder immediately prior to the closing of this offering upon the exchange of an equal number of Class B units held by the selling stockholder, together with the automatic retirement of an equal number of shares of our Class B common stock. We will not receive any proceeds from the sale of those shares.

Underwriters’ option to purchase additional shares						We will grant the underwriters an option, exercisable for 30 days after the date of this prospectus supplement, to purchase up to 1,275,000 additional shares of Class A common stock from us (and not from the selling stockholder) at the public offering price, less the underwriting discount.

Class A common stock to be outstanding after this offering						29,552,546 shares (or 30,827,546 shares, if the underwriters exercise in full their option to purchase additional shares of Class A common stock from us).

Class B common stock to be outstanding after this offering						36,902,216 shares (whether or not the underwriters exercise their option to purchase additional shares of Class A common stock).

Class A units to be held by us after this offering						29,552,546 Class A units (or 30,827,546 Class A units, if the underwriters exercise in full their option to purchase additional shares of Class A common stock from us), representing approximately 44.5% (or 45.5%, if the underwriters exercise in full their option to purchase additional shares of Class A common stock from us) of the economic interest in Viant Technology LLC.

Class B units to be held by us after this offering						0 Class B units, representing 0% of the economic interest in Viant Technology LLC.

Class B units to be held by the Continuing LLC Owners after this offering						36,902,216 Class B units, representing approximately 55.5% (or 54.5%, if the underwriters exercise in full their option to purchase additional shares of Class A common stock from us) of the economic interest in Viant Technology LLC.

Voting rights						Each share of Class A common stock and Class B common stock entitles its holder to one vote, voting as a single class on all matters submitted to a vote of our stockholders.

Use of proceeds						We will not receive any of the proceeds from the sale of shares of Class A common stock by the selling stockholder. If the underwriters exercise in full their option to purchase additional shares of Class A common stock from us, we estimate that the net proceeds to us will be approximately $ million, after deducting the underwriting discount and estimated offering expenses payable by us. We intend to use any net proceeds we receive from this offering for working capital, general corporate purposes and transaction expenses if the underwriters exercise their option to purchase additional shares of Class A common stock from us. See “Use of Proceeds.”

S-7


Risk factors						Investing in our Class A common stock involves a high degree of risk. See “Risk Factors” beginning on page S-9 of this prospectus supplement, and the other risk factors disclosed in our filings with the SEC that are incorporated by reference into this prospectus supplement and the accompanying prospectus, for a discussion of factors you should consider carefully before investing in our Class A common stock.

Nasdaq trading symbol						“DSP.”

Unless otherwise indicated, the number of shares outstanding after this offering is based on 21,052,546 shares of our Class A common stock and 45,402,216 shares of our Class B common stock outstanding as of June 30, 2026, and excludes:

•4.2 million shares of our Class A common stock issuable upon exercise of stock options outstanding as of June 30, 2026, which have a weighted-average exercise price of $6.05 per share;

•7.5 million shares of our Class A common stock issuable upon settlement of restricted stock units (“RSUs”) outstanding as of June 30, 2026;

•0.5 million shares of our Class A common stock issuable upon settlement of performance stock units (“PSUs”) outstanding as of June 30, 2026, assuming achievement of the applicable performance conditions at target;

•4.1 million shares of Class A common stock reserved for issuance under our 2021 Long-Term Incentive Plan as of June 30, 2026; and

•45.4 million shares of Class A common stock issuable upon the exchange of Class B units outstanding as of June 30, 2026 (which will be reduced by the 8,500,000 Class B units exchanged by the selling stockholder in connection with this offering).

Unless otherwise indicated, this prospectus supplement assumes no exercise of outstanding options, no settlement of outstanding RSUs or PSUs, and no exercise by the underwriters of their option to purchase additional shares of Class A common stock.

S-8

RISK FACTORS

Investment in any securities offered pursuant to this prospectus supplement and the accompanying prospectus involves a high degree of risk. Before deciding whether to invest in our Class A common stock, you should carefully consider the risks described below, together with the risk factors incorporated by reference from the 2025 10-K and our subsequent Quarterly Reports on Form 10-Q filed with the SEC, and all other information contained in or incorporated by reference into this prospectus supplement, as updated by our subsequent filings under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the risk factors and other information contained in the accompanying prospectus and any applicable free writing prospectus. The occurrence of any of these risks could cause you to lose all or part of your investment in the offered securities. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have a material adverse effect on our future results. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occur, our business, financial condition, results of operations or cash flows could be seriously harmed. This could cause the trading price of our Class A common stock to decline, resulting in a loss of all or part of your investment. Please also carefully read the section entitled “Cautionary Note Regarding Forward-Looking Statements” included in the 2025 10-K and our subsequent Quarterly Reports on Form 10-Q filed with the SEC.

Risks Related to This Offering

We will not receive any proceeds from the sale of shares of Class A common stock by the selling stockholder.

All of the shares of Class A common stock offered by this prospectus supplement, other than any shares sold upon exercise of the underwriters’ option to purchase additional shares, are being sold by the selling stockholder. We will not receive any of the proceeds from those sales, and none of those proceeds will be available to fund our operations, capital expenditures, compensation plans or acquisition opportunities. We will, however, bear a portion of the expenses of this offering. See “Use of Proceeds.”

Our management will have broad discretion in the use of any net proceeds we receive from this offering, and may not use them effectively.

We will receive net proceeds only if and to the extent the underwriters exercise their option to purchase additional shares of Class A common stock from us. Our management will have broad discretion in the application of any such net proceeds, and could spend or invest them in ways with which you may not agree. Accordingly, you will be relying on the judgment of our management with regard to the use of any net proceeds, and you will not have the opportunity, as part of your investment decision, to assess whether the proceeds are being used appropriately. It is possible that any net proceeds will be invested or otherwise used in a way that does not yield a favorable, or any, return for us, or that does not enhance the value of our Class A common stock.

If the underwriters exercise their option to purchase additional shares from us, you may experience dilution.

Any shares of Class A common stock that we sell upon exercise of the underwriters’ option to purchase additional shares will be newly issued shares. Their issuance may have a dilutive effect on our earnings per share and on the net tangible book value per share of the Class A common stock purchased in this offering. In addition, to the extent we issue additional equity or equity-linked securities in the future, including under our equity incentive plans or as consideration in acquisitions, our stockholders may experience further dilution.

Substantial future sales of our Class A common stock, or the perception that such sales may occur, could cause the market price of our Class A common stock to decline.

Sales of a substantial number of shares of our Class A common stock in the public market could occur at any time. As of June 30, 2026, there were 21,052,546 shares of our Class A common stock outstanding, 45,402,216 shares of our Class B common stock outstanding and 45,402,216 Class B units of Viant Technology LLC outstanding, which are exchangeable for an equivalent number of shares of our Class A common stock. If our stockholders sell, or the market perceives that our stockholders intend to sell, a substantial number of shares of our Class A common stock in the public market, the market price of our Class A common stock could decline

S-9

significantly. We and all of our directors and executive officers, as well as the selling stockholder, have agreed with the underwriters, subject to certain exceptions, not to dispose of or hedge any of our common stock or securities convertible into or exchangeable for shares of common stock during the period from the date of this prospectus supplement through the date 90 days after the date of the underwriting agreement. See “Underwriting” for a description of these restrictions and the exceptions thereto. Subject to these contractual restrictions, shares issued upon the exercise of stock options outstanding under our equity incentive plans or pursuant to future awards granted under those plans will become available for sale in the public market to the extent permitted by applicable vesting schedules and Rule 144 and Rule 701 under the Securities Act. If any of these additional shares are sold, or if it is perceived that they will be sold, in the public market, the market price of our Class A common stock could decline.

S-10

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus, the documents incorporated by reference into this prospectus supplement and other materials we have filed with the SEC contain forward-looking statements within the meaning of the federal securities laws. In some cases, you can identify forward-looking statements by words such as “may,” “should,” “expect,” “might,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential,” “seek,” “would” or “continue,” or the negative or plural of these words or other similar terms or expressions. All statements other than statements of historical fact are forward-looking statements, which speak only as of the date they are made, and are not guarantees of future performance. Forward-looking statements contained in this prospectus supplement or documents incorporated by reference into this prospectus supplement may include, but are not limited to, statements about: this offering, including the anticipated use of any net proceeds we receive; our future financial performance; trends in our key business measures; the sufficiency of our cash and cash equivalents and cash provided by sales of our products and services to meet our liquidity needs; market trends; our market position and opportunity; our growth strategy and business aspirations for our demand side platform in enabling the programmatic purchase of advertising in the digital advertising industry; our growth and product strategies, including our expectations relating to ViantAI; our efforts to enhance the security and privacy of our platform; the impact of information and data privacy trends and regulations on our business and competitors; the potential impacts of macroeconomic and geopolitical events on our business and the business of our customers, suppliers and channel partners, and the economy; payments under our Tax Receivable Agreement; repurchases of stock related to our stock repurchase program; our ability to attract new customers and retain existing customers; our ability to successfully expand into our existing markets and into new markets; our ability to effectively manage our growth and future expenses; our environmental and sustainability initiatives; the expected benefits of, and our integration of, the recently completed acquisition of TVision Insights, Inc.; the evaluation of our jurisdiction of incorporation and any potential reincorporation; and the impact of recent accounting pronouncements on our consolidated financial statements.

The forward-looking statements contained in this prospectus supplement or documents incorporated by reference into this prospectus supplement are based on historical performance and management’s current plans, estimates and expectations in light of information currently available to us and are subject to uncertainty and changes in circumstances. There can be no assurance that future developments affecting us will be those that we have anticipated. Actual results may differ materially from these expectations due to changes in global, regional or local political, economic, business, competitive, market, regulatory and other factors, many of which are beyond our control, as well as the other factors described in the section of this prospectus supplement and documents incorporated by reference into this prospectus supplement entitled “Risk Factors.” Additional factors or events that could cause our actual results to differ may also emerge from time to time, and it is not possible for us to predict all of them. Should one or more of these risks or uncertainties materialize, or should any of our assumptions prove to be incorrect, our actual results may vary in material respects from what we may have expressed or implied by these forward-looking statements. We may not actually achieve the plans, intentions, or expectations disclosed in our forward-looking statements, and we caution that you should not place undue reliance on any of our forward-looking statements. Any forward-looking statement made by us speaks only as of the date on which we make it. We undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by applicable securities laws. We claim the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995 for all forward-looking statements. You should read this prospectus supplement, and the documents that we reference in this prospectus supplement and have filed with the SEC, with the understanding that our actual future results, performance, and events and circumstances may be materially different from what we expect.

S-11

USE OF PROCEEDS

The shares of Class A common stock being sold by the selling stockholder are being sold for the account of the selling stockholder, and we will not receive any proceeds from the sale of those shares.

If the underwriters exercise in full their option to purchase additional shares of Class A common stock from us, we estimate that the net proceeds to us will be approximately $ million, after deducting the underwriting discount and estimated offering expenses payable by us.

We intend to use any net proceeds we receive from this offering to purchase newly issued Class A units of Viant Technology LLC at a per-unit price equal to the public offering price per share of our Class A common stock in this offering, less the underwriting discount. We intend to cause Viant Technology LLC to use such proceeds for working capital, general corporate purposes and transaction expenses if the underwriters exercise their option to purchase additional shares of Class A common stock from us. We may also cause Viant Technology LLC to use such proceeds to acquire businesses, assets or technologies or make other strategic investments, although we have no present commitments or agreements to enter into any such acquisitions or make any such investments.

Our management will have significant flexibility in applying any net proceeds we receive from this offering. The timing and amount of our actual expenditures will be based on many factors, including cash flows from operations and the anticipated growth of our business. Pending their use, we intend to cause Viant Technology LLC to invest any such net proceeds in short- and intermediate-term, interest-bearing, investment-grade securities.

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SELLING STOCKHOLDER

The table below sets forth information with respect to the beneficial ownership of our Class A common stock and Class B common stock for the selling stockholder.

Beneficial ownership is determined in accordance with SEC rules. The information is not necessarily indicative of beneficial ownership for any other purpose. In general, under these rules a beneficial owner of a security includes any person who, directly or indirectly, through any contract, arrangement, understanding, relationship or otherwise has or shares voting power or investment power with respect to such security. A person is also deemed to be a beneficial owner of a security if that person has the right to acquire beneficial ownership of such security within 60 days. To our knowledge, except as otherwise indicated, and subject to applicable community property laws, the persons named in the table have sole voting and investment power with respect to all shares of Class A common stock and Class B common stock beneficially owned by them.

In connection with our IPO, we issued to the Continuing LLC Owners one share of our Class B common stock for each Class B unit of Viant Technology LLC that they held. Each Continuing LLC Owner has the right to exchange its Class B units for an equivalent number of shares of our Class A common stock (together with the automatic retirement of such shares of our Class B common stock on a one-for-one basis with the number of Class B units so exchanged). In addition, we may also elect to satisfy such exchange for cash. The exchange by the selling stockholder of the Class B units underlying the shares offered by this prospectus supplement will be settled in shares of Class A common stock.

The number of shares of Class A common stock and Class B common stock outstanding and percentage of beneficial ownership before this offering set forth below are computed on the basis of 21,184,101 shares of our Class A common stock issued and outstanding as of August 31, 2026, and 45,314,716 shares of our Class B common stock issued and outstanding as of August 31, 2026. The number of shares of Class A common stock and Class B common stock and percentage of beneficial ownership after the consummation of this offering set forth below are based on the number of shares to be issued and outstanding immediately after the consummation of this offering. Shares of our Class A common stock that a person has the right to acquire within 60 days of August 31, 2026 (including the right to exchange described above) are deemed outstanding for purposes of computing the percentage ownership of such person’s holdings, but are not deemed outstanding for purposes of computing the percentage ownership of any other person.


	Class A Common Stock Beneficially Owned*								Class B Common Stock Beneficially Owned
Name of Beneficial Owner	Prior to this Offering		Number of Shares Sold in this Offering		After this Offering				Prior to this Offering			After this Offering
	Number	%	No Exercise of Option	With Full Exercise of Option	No Exercise of Option		With Full Exercise of Option					No Exercise of Option			With Full Exercise of Option
					Number	%	Number	%	Number	%		Number	%		Number	%
Capital V LLC(1)	—	—	—	—	—	—	—	—	27,209,326	60.0	%	18,709,326	50.8	%	18,709,326	50.8	%

__________________

*Reflects beneficial ownership of Class A common stock determined in accordance with Rule 13d-3(d)(1) of the Exchange Act.

(1)Each of Tim Vanderhook, Chris Vanderhook and Russ Vanderhook holds a one-third interest in Capital V LLC, representing an economic interest in (i) approximately 8,500,000 of the shares of Class A common stock offered by Capital V LLC in this offering and (ii) approximately 18,709,326 shares of Class B common stock and Class B units held by Capital V LLC after the consummation of this offering. Voting and investment decisions by Capital V LLC require the approval of a majority-in-interest of the members of Capital V LLC, and accordingly no individual has sole voting or investment control over the shares held by Capital V LLC.

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MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS TO NON-U.S. HOLDERS OF CLASS A COMMON STOCK

The following discussion is a summary of the material U.S. federal income tax consequences to Non-U.S. Holders (as defined below) of the purchase, ownership and disposition of our Class A common stock sold pursuant to this offering, but does not purport to be a complete analysis of all potential tax effects. The effects of other U.S. federal tax laws, such as estate and gift tax laws, and any applicable state, local or non-U.S. tax laws are not discussed. This discussion is based on the U.S. Internal Revenue Code of 1986, as amended (the “Code”), Treasury Regulations promulgated thereunder, judicial decisions and published rulings and administrative pronouncements of the U.S. Internal Revenue Service (the “IRS”), in each case in effect as of the date hereof. These authorities may change or be subject to differing interpretations. Any such change or differing interpretation may be applied retroactively in a manner that could adversely affect a Non-U.S. Holder. We have not sought and will not seek any rulings from the IRS regarding the matters discussed below. There can be no assurance the IRS or a court will not take a contrary position to that discussed below regarding the tax consequences of the purchase, ownership and disposition of our Class A common stock.

This discussion is limited to Non-U.S. Holders that hold our Class A common stock as a “capital asset” within the meaning of Section 1221 of the Code (generally, property held for investment). This discussion does not address all U.S. federal income tax consequences relevant to a Non-U.S. Holder’s particular circumstances, including the impact of the Medicare contribution tax on net investment income and the alternative minimum tax. In addition, it does not address consequences relevant to Non-U.S. Holders subject to special rules, including, without limitation:

•U.S. expatriates and former citizens or long-term residents of the United States;

•persons holding our Class A common stock as part of a hedge, straddle or other risk reduction strategy or as part of a conversion transaction or other integrated investment;

•banks, insurance companies and other financial institutions;

•brokers, dealers or traders in securities;

•“controlled foreign corporations,” “foreign controlled foreign corporations,” “passive foreign investment companies” and corporations that accumulate earnings to avoid U.S. federal income tax;

•partnerships or other entities or arrangements treated as partnerships for U.S. federal income tax purposes (and investors therein);

•tax-exempt organizations or governmental organizations;

•persons deemed to sell our Class A common stock under the constructive sale provisions of the Code;

•persons who hold or receive our Class A common stock pursuant to the exercise of any employee stock option or otherwise as compensation;

•tax-qualified retirement plans;

•“qualified foreign pension funds” as defined in Section 897(l)(2) of the Code and entities all of the interests of which are held by qualified foreign pension funds; and

persons subject to special tax accounting rules as a result of any item of gross income with respect to the stock being taken into account in an applicable financial statement.

If an entity or arrangement treated as a partnership for U.S. federal income tax purposes holds our Class A common stock, the tax treatment of a partner in the partnership will depend on the status of the partner, the activities of the partnership and certain determinations made at the partner level. Accordingly, partnerships holding our Class A common stock and the partners in such partnerships should consult their tax advisors regarding the U.S. federal income tax consequences to them.

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THIS DISCUSSION IS FOR INFORMATIONAL PURPOSES ONLY AND IS NOT TAX ADVICE. INVESTORS SHOULD CONSULT THEIR TAX ADVISORS WITH RESPECT TO THE APPLICATION OF THE U.S. FEDERAL INCOME TAX LAWS TO THEIR PARTICULAR SITUATIONS AS WELL AS ANY TAX CONSEQUENCES OF THE PURCHASE, OWNERSHIP AND DISPOSITION OF OUR CLASS A COMMON STOCK ARISING UNDER THE U.S. FEDERAL ESTATE OR GIFT TAX LAWS OR UNDER THE LAWS OF ANY STATE, LOCAL OR NON-U.S. TAXING JURISDICTION OR UNDER ANY APPLICABLE INCOME TAX TREATY.

Definition of a Non-U.S. Holder

For purposes of this discussion, a “Non-U.S. Holder” is any beneficial owner of our Class A common stock that is neither a “U.S. person” nor an entity or arrangement treated as a partnership for U.S. federal income tax purposes. A U.S. person is any person that, for U.S. federal income tax purposes, is or is treated as any of the following:

•an individual who is a citizen or resident of the United States;

•a corporation created or organized under the laws of the United States, any state thereof or the District of Columbia;

•an estate, the income of which is subject to U.S. federal income tax regardless of its source; or

•a trust that (1) is subject to the primary supervision of a U.S. court and the control of one or more “United States persons” (within the meaning of Section 7701(a)(30) of the Code), or (2) has a valid election in effect to be treated as a United States person for U.S. federal income tax purposes.

Distributions

If we make distributions of cash or property on our Class A common stock, such distributions will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Amounts not treated as dividends for U.S. federal income tax purposes will constitute a return of capital and first be applied against and reduce a Non-U.S. Holder’s adjusted tax basis in its Class A common stock, but not below zero. Any excess will be treated as capital gain and will be treated as described below under “—Sale or Other Taxable Disposition.”

Subject to the discussions below on effectively connected income, information reporting and backup withholding and additional withholding tax on payments made to foreign accounts, dividends paid to a Non-U.S. Holder will be subject to U.S. federal withholding tax at a rate of 30% of the gross amount of the dividends (or such lower rate specified by an applicable income tax treaty, provided the Non-U.S. Holder furnishes a valid IRS Form W-8BEN or W-8BEN-E (or other applicable documentation) certifying qualification for the lower treaty rate). A Non-U.S. Holder that does not timely furnish the required documentation, but that qualifies for a reduced treaty rate, may obtain a refund of any excess amounts withheld by timely filing an appropriate claim for refund with the IRS. Non-U.S. Holders should consult their tax advisors regarding their entitlement to benefits under any applicable income tax treaty.

If dividends paid to a Non-U.S. Holder are effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States (and, if required by an applicable income tax treaty, the Non-U.S. Holder maintains a permanent establishment in the United States to which such dividends are attributable), the Non-U.S. Holder will be exempt from the U.S. federal withholding tax described above. To claim the exemption, the Non-U.S. Holder must furnish to the applicable withholding agent a valid IRS Form W-8ECI, certifying that the dividends are effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States.

Any such effectively connected dividends will be subject to U.S. federal income tax on a net income basis at the regular rates. A Non-U.S. Holder that is a corporation also may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on such effectively connected dividends, as adjusted for certain items. Non-U.S. Holders should consult their tax advisors regarding any applicable tax treaties that may provide for different rules.

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Sale or Other Taxable Disposition

A Non-U.S. Holder will not be subject to U.S. federal income tax on any gain realized upon the sale or other taxable disposition of our Class A common stock unless:

•the gain is effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States (and, if required by an applicable income tax treaty, the Non-U.S. Holder maintains a permanent establishment in the United States to which such gain is attributable);

•the Non-U.S. Holder is a nonresident alien individual present in the United States for 183 days or more during the taxable year of the disposition and certain other requirements are met; or

•our Class A common stock constitutes a U.S. real property interest (“USRPI”) by reason of our status as a U.S. real property holding corporation (“USRPHC”) for U.S. federal income tax purposes.

Gain described in the first bullet point above generally will be subject to U.S. federal income tax on a net income basis at the regular rates. A Non-U.S. Holder that is a corporation also may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on such effectively connected gain, as adjusted for certain items.

A Non-U.S. Holder described in the second bullet point above will be subject to U.S. federal income tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on gain realized upon the sale or other taxable disposition of our Class A common stock, which may be offset by U.S. source capital losses of the Non-U.S. Holder (even though the individual is not considered a resident of the United States), provided the Non-U.S. Holder has timely filed U.S. federal income tax returns with respect to such losses.

With respect to the third bullet point above, we believe we currently are not, and do not anticipate becoming, a USRPHC. Generally, a corporation is a USRPHC if the fair market value of its United States real property interests equals or exceeds 50% of the sum of the fair market value of its worldwide real property interests and its other assets used or held for use in a trade or business. Because the determination of whether we are a USRPHC depends, however, on the fair market value of our USRPIs relative to the fair market value of our non-U.S. real property interests and our other business assets, there can be no assurance we currently are not a USRPHC or will not become one in the future. Even if we are or were to become a USRPHC, gain arising from the sale or other taxable disposition of our Class A common stock by a Non-U.S. Holder will not be subject to U.S. federal income tax if our Class A common stock is “regularly traded,” as defined by applicable Treasury Regulations, on an established securities market and such Non-U.S. Holder owned, actually and constructively, 5% or less of our Class A common stock throughout the shorter of the five-year period ending on the date of the sale or other taxable disposition or the Non-U.S. Holder’s holding period.

Non-U.S. Holders should consult their tax advisors regarding potentially applicable income tax treaties that may provide for different rules.

Information Reporting and Backup Withholding

Payments of dividends on our Class A common stock will not be subject to backup withholding, provided the applicable withholding agent does not have actual knowledge or reason to know the holder is a United States person and the holder either certifies its non-U.S. status, such as by furnishing a valid IRS Form W-8BEN, W-8BEN-E or W-8ECI, or otherwise establishes an exemption. However, information returns are required to be filed with the IRS in connection with any distributions on our Class A common stock paid to the Non-U.S. Holder, regardless of whether such distributions constitute dividends or whether any tax was actually withheld. In addition, proceeds of the sale or other taxable disposition of our Class A common stock within the United States or conducted through certain U.S.-related brokers generally will not be subject to backup withholding or information reporting if the applicable withholding agent receives the certification described above and does not have actual knowledge or reason to know that such holder is a United States person or the holder otherwise establishes an exemption. Proceeds of a disposition of our Class A common stock conducted through a non-U.S. office of a non-U.S. broker generally will not be subject to backup withholding or information reporting.

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Copies of information returns that are filed with the IRS may also be made available under the provisions of an applicable treaty or agreement to the tax authorities of the country in which the Non-U.S. Holder resides or is established.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a Non-U.S. Holder’s U.S. federal income tax liability, provided the required information is timely furnished to the IRS.

Additional Withholding Tax on Payments Made to Foreign Accounts

Withholding taxes may be imposed under Sections 1471 to 1474 of the Code (such Sections commonly referred to as the Foreign Account Tax Compliance Act, or “FATCA”) on certain types of payments made to non-U.S. financial institutions and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on dividends on, or (subject to the proposed Treasury Regulations discussed below) gross proceeds from the sale or other disposition of, our Class A common stock paid to a “foreign financial institution” or a “non-financial foreign entity” (each as defined in the Code), unless (1) the foreign financial institution undertakes certain diligence and reporting obligations, (2) the non-financial foreign entity either certifies it does not have any “substantial United States owners” (as defined in the Code) or furnishes identifying information regarding each substantial United States owner or (3) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules. If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in (1) above, it must enter into an agreement with the U.S. Department of the Treasury requiring, among other things, that it undertake to identify accounts held by certain “specified United States persons” or “United States owned foreign entities” (each as defined in the Code), annually report certain information about such accounts and withhold 30% on certain payments to non-compliant foreign financial institutions and certain other account holders. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules.

Under the applicable Treasury Regulations and administrative guidance, withholding under FATCA generally applies to payments of dividends on our Class A common stock. While withholding under FATCA would have applied under these Treasury Regulations also to payments of gross proceeds from the sale or other disposition of our Class A common stock on or after January 1, 2019, proposed Treasury Regulations eliminate FATCA withholding on payments of gross proceeds entirely. Taxpayers generally may rely on these proposed Treasury Regulations until final Treasury Regulations are issued.

Prospective investors should consult their tax advisors regarding the potential application of withholding under FATCA to their investment in our Class A common stock.

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UNDERWRITING

Evercore Group L.L.C. and Wells Fargo Securities, LLC (collectively, the “Representatives”) are acting as lead book-running managers of the offering and representatives of the underwriters named below.

We, the selling stockholder and the underwriters named below will enter into an underwriting agreement with respect to the shares being offered. Subject to the terms and conditions stated in the underwriting agreement, each underwriter named below will severally agree to purchase, and the selling stockholder will agree to sell to the underwriters, the number of shares of Class A common stock set forth opposite the underwriter’s name in the following table:


Underwriter						Number of Shares
Evercore Group L.L.C.
Wells Fargo Securities, LLC
RBC Capital Markets, LLC
Craig-Hallum Capital Group LLC
Total

The underwriting agreement will provide that the obligations of the underwriters to purchase the shares of our Class A common stock included in this offering are subject to approval of legal matters by counsel and to other conditions. The underwriters will be obligated to purchase all of the shares of our Class A common stock (other than those covered by the underwriters’ option to purchase additional shares described below) if they purchase any of the shares.

Shares of our Class A common stock sold by the underwriters to the public will initially be offered at the public offering price set forth on the cover of this prospectus supplement. Any shares of our Class A common stock sold by the underwriters to securities dealers may be sold at a discount from the public offering price not to exceed $ per share. After the initial offering of the shares of our Class A common stock, the Representatives may change the offering price and the other selling terms. The offering of the shares by the underwriters is subject to receipt and acceptance and subject to the underwriters’ right to reject any order in whole or in part. The Representatives have advised us and the selling stockholder that the underwriters do not intend to make sales to discretionary accounts.

We will grant to the underwriters an option, exercisable for 30 days after the date of this prospectus supplement, to purchase, from time to time, in whole or in part, up to an aggregate of 1,275,000 shares of our Class A common stock from us at the public offering price set forth on the cover of this prospectus supplement, less underwriting discounts and commissions. If the underwriters exercise this option, each underwriter will be obligated, subject to specified conditions, to purchase a number of additional shares proportionate to that underwriter’s initial purchase commitment as indicated in the table above. Any shares of our Class A common stock sold under the option will be sold on the same terms and conditions as the other shares of our Class A common stock that are the subject of this offering.

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Commissions and Expenses

The following table shows the per share and total underwriting discounts and commissions to be paid to the underwriters by us and the selling stockholder. These amounts are shown assuming both no exercise and full exercise of the underwriters’ option to purchase additional shares.

No Exercise

Full Exercise

(dollars in thousands)

Paid by us

Per Share

—

Total

—

Paid by the selling stockholder

Per Share

Total

We estimate that expenses payable by us in connection with this offering, exclusive of underwriting discounts and commissions, will be approximately $0.5 million. We will also agree to reimburse the underwriters for expenses in an amount not to exceed $20,000 relating to any applicable state securities filings and to clearance of this offering with the Financial Industry Regulatory Authority. We and the selling stockholder will also agree to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act.

Lock-up Agreements

In connection with this offering, we, all of our directors and officers and the selling stockholder will agree that, subject to certain exceptions, during the period beginning on the date of this prospectus supplement and ending 90 days after that date (the “Lock-Up Period”), we and they will not, without the prior written consent of the Representatives (i) directly or indirectly, offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise transfer or dispose of any shares of Class A common stock, units of Viant Technology LLC or any securities convertible into or exercisable or exchangeable for Class A common stock or such units, whether now owned or later acquired or over which they have or later acquire the power of disposition (collectively, the “Lock-Up Securities”), exercise any right with respect to the registration of any Lock-Up Securities, or file, cause to be filed or cause to be confidentially submitted any registration statement in connection therewith under the Securities Act, (ii) enter into any swap or other agreement or transaction that transfers, in whole or in part, directly or indirectly, the economic consequences of ownership of the Lock-Up Securities, whether any such swap or transaction is to be settled by delivery of Class A common stock, units of Viant Technology LLC or other securities, in cash or otherwise, or (iii) publicly announce the intention to do any of the foregoing.

The lock-up restrictions above that apply to us do not apply to (A) the shares of Class A common stock to be sold in this offering, (B) shares of Class A common stock issued upon the exercise of an option or warrant or the conversion of a security outstanding on the date hereof and referred to in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference herein, (C) shares of Class A common stock, options to purchase Class A common stock, restricted stock units covering shares of Class A common stock or other equity incentive awards granted under our existing employee benefit plans or equity incentive plans referred to in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference herein, (D) shares of Class A common stock issued pursuant to any non-employee director stock plan referred to in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference herein, (E) our filing of a registration statement on Form S-8, or any successor form, with respect to securities to be offered under any of those employee benefit or equity incentive plans, or (F) the issuance of up to 10% of our total outstanding shares of Class A common stock in connection with the acquisition of the assets of, or a majority or controlling portion of the equity of, or a joint venture, other commercial relationship or strategic alliance with, another entity, provided that each recipient of shares issued or sold under clause (F) during the Lock-Up Period agrees to be bound by lock-up restrictions substantially the same as those described above for the remainder of the Lock-Up Period.

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With respect to the lock-up agreements entered into by our directors and officers and the selling stockholder, the restrictions described in the preceding paragraphs will not apply to transfers or other dispositions of Lock-Up Securities:

(i)as a bona fide gift or gifts or charitable contribution;

(ii)to any trust, partnership, limited liability company or other entity for the direct or indirect benefit of such person or such person’s immediate family, or to a member of such person’s immediate family (meaning any relationship by blood, marriage or adoption no more remote than first cousin), or, in the case of a trust, to its beneficiaries or estate;

(iii)as a distribution to limited partners, partners, members, stockholders or other equityholders of such person;

(iv)to such person’s affiliates or to any investment fund or other entity controlled or managed by such person;

(v)the exchange of units of Viant Technology LLC (or securities convertible into or exercisable or exchangeable for those units), together with the surrender and cancellation of a corresponding number of shares of Class B common stock, for shares of Class A common stock (or securities convertible into or exercisable or exchangeable for Class A common stock) pursuant to the operating agreement of Viant Technology LLC or other agreements described in this prospectus supplement or the documents incorporated by reference herein;

(vi)by will, other testamentary document or intestate succession upon death, or for bona fide estate planning purposes;

(vii)by operation of law, such as pursuant to an order of a court or regulatory agency of competent jurisdiction, a qualified domestic relations order or a divorce settlement;

(viii)to us upon exercise of any right in respect of any equity award granted under any of our incentive plans described in the final prospectus relating to this offering, including the surrender of shares of Class A common stock to us in a “net” or “cashless” exercise or settlement of an equity award;

(ix)to a bona fide third party in a merger, consolidation, tender offer or other similar transaction that is made to all holders of Class A common stock, is approved by our board of directors and would result in a person or group of affiliated persons (other than an underwriter in this offering) holding more than 50% of our outstanding voting securities (or those of the surviving entity), provided that if the transaction is not completed, and with respect to any shares not transferred in the transaction, the Lock-Up Securities will remain subject to the lock-up restrictions;

(x)pursuant to a written plan meeting the requirements of Rule 10b5-1 under the Exchange Act, that was established before the execution of the underwriting agreement;

(xi)to a nominee or custodian of a person or entity to whom a disposition or transfer would be permitted under clauses (i) through (iv), (vi) or (vii) above;

(xii)pursuant to the sale or other transfer of Lock-Up Securities, or a broker-assisted sale or cashless exercise, to satisfy any tax obligations or payments (including the payment of exercise prices) due as a result of the exercise of stock options that will expire during the Lock-Up Period, provided that (1) any securities received upon the exercise that are not sold or transferred to cover those tax or payment obligations will remain subject to the lock-up restrictions and (2) the stock options are held pursuant to an agreement or equity awards granted under a stock incentive plan or other equity award plan; or

(xiii)pursuant to sales in open market transactions during the Lock-Up Period to generate such amount of net proceeds from those sales (after deducting commissions) in an aggregate amount up to the total amount of taxes or estimated taxes (as applicable) that become due as a result of the vesting and/or settlement of

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our equity awards held by such person that vest and/or settle during the Lock-Up Period, provided that any Lock-Up Securities retained by such person after giving effect to this provision will remain subject to the lock-up restrictions.

In the case of any transfer under the above clauses, other than clause (ix), (1) the transferred securities, and any securities received in connection with the transfer, must remain subject to the lock-up restrictions or the Representatives must receive a signed lock-up agreement from the donee, trustee, distributee or transferee, (2) the transfer may not involve a disposition for value, (3) the transfer may not be required to be reported to the SEC on Form 4 or Form 5 under Section 16(a) of the Exchange Act, except in the case of clauses (i), (v) through (viii), (x), (xii) and (xiii) in which case the filing must clearly indicate in a footnote the circumstances of the particular transfer, and (4) the transferor may not otherwise voluntarily effect any public filing or report regarding the transfer.

These lock-up agreements will not prevent the establishment of a Rule 10b5-1 trading plan, or the amendment or termination of an existing plan, so long as the plan does not provide for sales of Lock-Up Securities during the Lock-Up Period and any public announcement or filing regarding the plan states that no transfer of Lock-Up Securities may be made under the plan during the Lock-Up Period. Our directors and officers and the selling stockholder may also sell shares of Class A common stock purchased on the open market following this offering if the sales are not required to be reported in any public report or filing with the SEC or otherwise and no public filing or report regarding the sales is voluntarily made.

The Representatives, in their sole discretion, may release any of the securities subject to these lock-up agreements at any time. If the Representatives release or waive the restrictions for one of our officers or directors, we will announce the release or waiver through a major news service at least two business days before its effective date.

Determination of Offering Price

There is a public market for our Class A common stock. The offering price for the shares will be negotiated among us and the Representatives. Among the factors considered in determining the public offering price will be our results of operations, our current financial condition, our future prospects, our markets, the economic conditions in and future prospects for the industry in which we compete, our management and currently prevailing general conditions in the equity securities markets, including current market valuations of companies in related businesses.

Listing

Our Class A common stock is listed on Nasdaq under the symbol “DSP.”

Stabilization

In connection with this offering, the underwriters may purchase and sell shares of our Class A common stock in the open market. Purchases and sales in the open market may include short sales, purchases to cover short positions, which may include purchases pursuant to the underwriters’ option to purchase additional shares, and stabilizing purchases.

•Short sales involve secondary market sales by the underwriters of a greater number of shares of our Class A common stock than they are required to purchase in this offering.

•“Covered” short sales are sales of shares of our Class A common stock in an amount up to the number of shares of our Class A common stock represented by the underwriters’ option to purchase additional shares.

•“Naked” short sales are sales of shares of our Class A common stock in an amount in excess of the number of shares of our Class A common stock represented by the underwriters’ option to purchase additional shares.

•Covering transactions involve purchases of shares either pursuant to the underwriters’ option to purchase additional shares or in the open market.

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•To close a naked short position, the underwriters must purchase shares of our Class A common stock in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the shares of our Class A common stock in the open market after pricing that could adversely affect investors who purchase in this offering.

•To close a covered short position, the underwriters must purchase shares of our Class A common stock in the open market or exercise the option to purchase additional shares. In determining the source of shares of our Class A common stock to close the covered short position, the underwriters will consider, among other things, the price of shares of our Class A common stock available for purchase in the open market as compared to the price at which they may purchase shares of our Class A common stock through the option.

•Stabilizing transactions involve bids of our Class A common stock on Nasdaq to purchase shares, as long as the stabilizing bids do not exceed a specified maximum.

The underwriters may also impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the Representatives have repurchased shares sold by or for the account of such underwriter in stabilizing or short covering transactions. Purchases to cover short positions and stabilizing purchases, as well as other purchases by the underwriters for their own accounts, may have the effect of preventing or retarding a decline in the market price of the shares. Together with the imposition of the penalty bid, such purchases may stabilize, maintain or otherwise affect the market price of the Class A common stock. As a result, the price of the Class A common stock may be higher than the price that would otherwise exist in the open market in the absence of these transactions. The underwriters may conduct these transactions on Nasdaq, in the over-the-counter market or otherwise. The underwriters are not required to engage in any of these activities and, if they do commence any, they may discontinue them at any time.

Electronic Distribution

A prospectus in electronic format may be made available on websites maintained by one or more of the underwriters or their respective affiliates. The Representatives may agree with us to allocate a number of shares of our Class A common stock to underwriters for sale to their online brokerage account holders. Any such allocation for online distributions will be made by the underwriters on the same basis as other allocations. Other than the prospectus in electronic format, the information on the underwriters’ or their respective affiliates’ websites and any information contained in any other website maintained by any of the underwriters or their respective affiliates is not part of this prospectus, has not been approved and/or endorsed by us or the underwriters and should not be relied upon by investors in this offering.

Other Activities and Relationships

The underwriters and their respective affiliates are full-service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. Certain of the underwriters and their respective affiliates may, from time to time, engage in transactions with and perform services for us in the ordinary course of their business for which they may receive customary fees and reimbursement of expenses. In the ordinary course of their various business activities, the underwriters and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (which may include bank loans and/or credit default swaps) for their own account and for the accounts of their customers, and may at any time hold long and short positions in such securities and instruments. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

The sellers of the shares of our Class A common stock have not authorized and do not authorize the making of any offer of shares of our Class A common stock through any financial intermediary on their behalf, other than offers made by the underwriters with a view to the final placement of the shares of our Class A common stock as contemplated in this prospectus supplement. Accordingly, no purchaser of the shares of our Class A common stock,

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other than the underwriters, is authorized to make any further offer of the shares of our Class A common stock on behalf of the sellers or the underwriters.

Selling Restrictions

Notice to Prospective Investors in the European Economic Area

In relation to each Member State of the European Economic Area (each a “Relevant State”), no shares of Class A common stock have been offered or will be offered pursuant to this offering to the public in that Relevant State prior to the publication of a prospectus in relation to the shares of our Class A common stock which has been approved by the competent authority in that Relevant State or, where appropriate, approved in another Relevant State and notified to the competent authority in that Relevant State, all in accordance with Regulation (EU) 2017/1129 (the “Prospectus Regulation”), except that offers of shares of Class A common stock may be made to the public in that Relevant State at any time under the following exemptions under the Prospectus Regulation:

a)to any qualified investor as defined under the Prospectus Regulation;

b)to fewer than 150 natural or legal persons (other than qualified investors as defined under the Prospectus Regulation), subject to obtaining the prior consent of the Representatives for any such offer; or

c)in any other circumstances falling within Article 1(4) of the Prospectus Regulation,

provided that no such offer of shares of Class A common stock shall require us or any underwriter to publish a prospectus pursuant to Article 3 of the Prospectus Regulation or supplement a prospectus pursuant to Article 23 of the Prospectus Regulation or publish an Annex IX document pursuant to Article 1(4) of the Prospectus Regulation.

For the purposes of this provision, the expression an “offer to the public” in relation to any shares of Class A common stock in any Relevant State means the communication in any form and by any means of sufficient information on the terms of the offer and any shares of Class A common stock to be offered so as to enable an investor to decide to purchase or subscribe for any shares of Class A common stock.

The above selling restriction is in addition to any other selling restrictions set out below.

Notice to Prospective Investors in the United Kingdom

In relation to the United Kingdom (the "UK"), no shares of Class A common stock have been offered or will be offered pursuant to this offering to the public in the UK, except that offers of shares of Class A common stock may be made to the public in the UK at any time:

a)where (i) the offer is conditional on the admission of the shares of Class A common stock to trading on the London Stock Exchange plc’s main market (in reliance on the exception in paragraph 6(a) of

Schedule 1 of the POATR) or (ii) the shares of Class A common stock being offered are at the time of the offer already admitted to trading on the London Stock Exchange plc’s main market (in reliance on the exception in paragraph 6(b) of Schedule 1 of the POATR);

b)to any qualified investor as defined in paragraph 15 of the POATR;

c)to fewer than 150 persons (other than qualified investors as defined in paragraph 15 of Schedule 1 of the POATR), subject to obtaining the prior consent of the Representatives for any such offer; or

d)at any time in other circumstances falling within Part 1 of Schedule 1 of the POATR.

For the purposes of this provision, the expression an “offer to the public” in relation to any shares of Class A common stock in the UK means the communication to any person which presents sufficient information on the shares of Class A common stock to be offered and the terms on which they are to be offered, to enable an investor to decide to buy or subscribe for the shares of Class A common stock, and the expression “POATR” means Public Offers and Admissions to Trading Regulations 2024.

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Notice to Prospective Investors in Israel

This prospectus does not constitute a prospectus as defined under the Israeli Securities Law, 5728-1968 (the “Israeli Securities Law”), and has not been filed with or approved by the Israel Securities Authority.

In Israel, this prospectus is being distributed only to, and is directed only at, and any offer of the shares of our Class A common stock is directed only at, (i) a limited number of persons in accordance with the Israeli Securities Law and (ii) investors listed in the first addendum (as it may be amended from time to time, the “Addendum”), to the Israeli Securities Law, consisting primarily of joint investment in trust funds, provident funds, insurance companies, banks, portfolio managers, investment advisors, members of the Tel Aviv Stock Exchange, underwriters, venture capital funds, entities with equity in excess of NIS 50 million and “qualified individuals,” each as defined in the Addendum, collectively referred to as qualified investors (in each case, purchasing for their own account or, where permitted under the Addendum, for the accounts of their clients who are investors listed in the Addendum). Qualified investors are required to submit written confirmation that they fall within the scope of the Addendum, are aware of the meaning of same and agree to it.

Notice to Prospective Investors in France

Neither this prospectus nor any other offering material relating to the shares of our Class A common stock described in this prospectus has been submitted to the clearance procedures of the Autorité des Marchés Financiers or of the competent authority of another member state of the European Economic Area and notified to the Autorité des Marchés Financiers. The shares of our Class A common stock have not been offered or sold and will not be offered or sold, directly or indirectly, to the public in France. Neither this prospectus nor any other offering material relating to the shares of our Class A common stock has been or will be:

a)released, issued, distributed or caused to be released, issued or distributed to the public in France; or

b)used in connection with any offer for subscription or sale of the shares of our Class A common stock to the public in France.

Such offers, sales and distributions will be made in France only:

a)to qualified investors (investisseurs qualifiés) and/or to a restricted circle of investors (cercle restreint d’investisseurs), in each case investing for their own account, all as defined in, and in accordance with, articles L.411-2, D.411-1, D.411-2, D.734-1, D.744-1, D.754-1 and D.764-1 of the French Code monétaire et financier;

b)to investment services providers authorized to engage in portfolio management on behalf of third parties; or

c)in a transaction that, in accordance with article L.411-2-II-1° -or- 2° -or 3° of the French Code monétaire et financier and article 211-2 of the General Regulations (Règlement Général) of the Autorité des Marchés Financiers, does not constitute a public offer (appel public à l’épargne).

The shares of our Class A common stock may be resold directly or indirectly, only in compliance with articles L.411-1, L.411-2, L.412-1 and L.621-8 through L.621-8-3 of the French Code monétaire et financier.

Notice to Prospective Investors in Hong Kong

The shares of our Class A common stock have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance; or (b) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies Ordinance (Cap. 32) of Hong Kong or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the shares of our Class A common stock has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to the shares of our Class A common stock which

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are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance and any rules made under that Ordinance.

Notice to Prospective Investors in Japan

The shares of our Class A common stock have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948, as amended) and, accordingly, will not be offered or sold, directly or indirectly, in Japan, or for the benefit of any Japanese Person or to others for reoffering or resale, directly or indirectly, in Japan or to any Japanese Person, except in compliance with all applicable laws, regulations and ministerial guidelines promulgated by relevant Japanese governmental or regulatory authorities in effect at the relevant time. For the purposes of this paragraph, “Japanese Person” shall mean any person resident in Japan, including any corporation or other entity organized under the laws of Japan.

Notice to Prospective Investors in Singapore

This prospectus has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, the shares of our Class A common stock were not offered or sold or caused to be made the subject of an invitation for subscription or purchase and will not be offered or sold or caused to be made the subject of an invitation for subscription or purchase, and this prospectus or any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the shares of our Class A common stock, has not been circulated or distributed, nor will it be circulated or distributed, whether directly or indirectly, to any person in Singapore other than (i) to an institutional investor (as defined in Section 4A of the Securities and Futures Act 2001 of Singapore, as modified or amended from time to time (the "SFA")) pursuant to Section 274 of the SFA, (ii) to a relevant person (as defined in Section 275(2) of the SFA) pursuant to Section 275(1) of the SFA, or any person pursuant to Section 275(1A) of the SFA, and in accordance with the conditions specified in Section 275 of the SFA, or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Singapore SFA Product Classification: In connection with Section 309B of the SFA and the CMP Regulations 2018, unless otherwise specified before an offer of the shares of our Class A common stock, we have determined, and hereby notify all relevant persons (as defined in Section 309A(1) of the SFA), that the shares of our Class A common stock are “prescribed capital markets products” (as defined in the CMP Regulations 2018) and Excluded Investment Products (as defined in MAS Notice SFA 04-N12: Notice on the Sale of Investment Products and MAS Notice FAA-N16: Notice on Recommendations on Investment Products).

Notice to Prospective Investors in Switzerland

The offering of the shares of Class A common stock in Switzerland is exempt from the requirement to prepare and publish a prospectus under the Swiss Financial Services Act (“FinSA”) because such offering is made to professional clients within the meaning of the FinSA only, and the shares of Class A common stock will not be admitted to trading on any trading venue (exchange or multilateral trading facility) in Switzerland. This document does not constitute a prospectus pursuant to the FinSA, and no such prospectus has been or will be prepared for or in connection with the offering of the shares of Class A common stock.

Notice to Prospective Investors in Dubai International Financial Centre (“DIFC”)

This prospectus relates to an exempt offer which is not subject to any form of regulation or approval by the Dubai Financial Services Authority (the “DFSA”). The DFSA has not approved this prospectus nor has any responsibility for reviewing or verifying any document or other documents in connection with the offering. Accordingly, the DFSA has not approved this prospectus or any other associated documents nor taken any steps to verify the information set out in this prospectus, and has no responsibility for it.

The shares of Class A common stock have not been offered and will not be offered to any persons in the DIFC except on the basis that an offer is:

(i)an “Exempt Offer” in accordance with the Markets Rules (MKT) Module of the DFSA Rulebook; and

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(ii)made only to persons who meet the “Deemed Professional Client” criteria set out in Rule 2.3.4 of the Conduct of Business (COB) module of the DFSA Rulebook, who are not natural persons.

Notice to Prospective Investors in Canada

The shares of Class A common stock may be sold only to purchasers purchasing, or deemed to be purchasing, as principal, that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions, and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the shares of Class A common stock must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 (or, in the case of securities issued or guaranteed by the government of a non-Canadian jurisdiction, section 3A.4) of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Notice to Prospective Investors in Australia

No placement document, prospectus, product disclosure statement, or other disclosure document has been lodged with the Australian Securities and Investments Commission in relation to the offering. This offering document does not constitute a prospectus, product disclosure statement or other disclosure document under the Corporations Act 2001 (the "Corporations Act") and does not purport to include the information required for a prospectus, product disclosure statement or other disclosure document under the Corporations Act.

Any offer in Australia of the shares may only be made to persons (the "Exempt Investors") who are “sophisticated investors” (within the meaning of section 708(8) of the Corporations Act), “professional investors” (within the meaning of section 708(11) of the Corporations Act), or otherwise pursuant to one or more exemptions contained in section 708 of the Corporations Act so that it is lawful to offer the shares without disclosure to investors under Chapter 6D of the Corporations Act.

The shares applied for by Exempt Investors in Australia must not be offered for sale in Australia in the period of 12 months after the date of allotment under the offering, except in circumstances where disclosure to investors under Chapter 6D of the Corporations Act would not be required pursuant to an exemption under section 708 of the Corporations Act or otherwise, or where the offer is pursuant to a disclosure document which complies with Chapter 6D of the Corporations Act. Any person acquiring shares must observe such Australian on-sale restrictions.

This offering document contains general information only and does not take account of the investment objectives, financial situation, or particular needs of any particular person. It does not contain any securities recommendations or financial product advice. Before making an investment decision, investors need to consider whether the information in this offering document is appropriate to their needs, objectives and circumstances, and, if necessary, seek expert advice on those matters.

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LEGAL MATTERS

Certain legal matters in connection with this offering will be passed upon for us by Latham & Watkins LLP. Certain legal matters in connection with this offering will be passed upon for the underwriters by Fenwick & West LLP, Santa Monica, California.

EXPERTS

The financial statements of Viant Technology Inc. as of December 31, 2025 and 2024, and for each of the three years in the period ended December 31, 2025, incorporated in this prospectus supplement by reference to Viant Technology Inc.’s Annual Report on Form 10-K for the year ended December 31, 2025, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report. Such financial statements are incorporated by reference in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the shares of Class A common stock offered hereby. This prospectus supplement, which constitutes part of the registration statement, does not contain all of the information set forth in the registration statement and the exhibits and schedules thereto. For further information with respect to us and the shares of Class A common stock offered hereby, you should refer to the registration statement and to the exhibits and schedules filed therewith. Statements contained in this prospectus supplement regarding the contents of any contract or any other document that is filed as an exhibit to the registration statement are not necessarily complete, and each such statement is qualified in all respects by reference to the full text of such contract or other document filed as an exhibit to the registration statement. We are also required to file annual, quarterly and current reports, proxy statements and other information with the SEC, copies of which are available free of charge on the SEC’s website, www.sec.gov.

You may obtain a copy of any of our filings, at no cost, by writing or telephoning us at:

Viant Technology Inc.

2722 Michelson Drive, Suite 100

Irvine, CA 92612

(949) 861-8888

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INCORPORATION OF DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” information we file with it into the registration statement of which this prospectus supplement forms a part, which means that we can disclose important information to you by referring you to other documents. The information incorporated by reference is considered to be part of this prospectus supplement. We incorporate by reference into this prospectus supplement the documents listed below, except for information “furnished” under Items 2.02 or 7.01 of Form 8-K or other information “furnished” to the SEC, which is not deemed filed and is not incorporated by reference into this prospectus supplement.

We hereby incorporate by reference the following documents:

(a)Our Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on March 11, 2026;

(b)The information specifically incorporated by reference into our Annual Report on Form 10-K for the year ended December 31, 2025 from our Definitive Proxy Statement on Schedule 14A, filed with the SEC on April 23, 2026;

(c)Our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2026 and June 30, 2026, filed with the SEC on May 11, 2026 and August 10, 2026, respectively;

(d)Our Current Reports on Form 8-K filed with the SEC on April 15, 2026 (other than the portions furnished under Item 2.02), June 5, 2026 and August 10, 2026 (only with respect to Item 5.02); and

(e)The description of our Class A common stock incorporated by reference in our registration statement on Form 8-A (File No. 001-40015), dated February 5, 2021, filed with the SEC on February 5, 2021, and any amendment or report filed with the SEC for the purpose of updating such description.

We will provide to each person, including any beneficial owner, to whom a prospectus is delivered, upon written or oral request of any such person, a copy of the reports and documents that have been incorporated by reference into this prospectus supplement, at no cost. Any such request should be directed to: Viant Technology Inc., 2722 Michelson Drive, Suite 100, Irvine, CA 92612. These documents are also available on the Investor Relations section of our website, which is located at www.viantinc.com, or as described under “Where You Can Find More Information” above. The reference to our website address does not constitute incorporation by reference of the information contained on our website, and information contained on, or accessible through, our website is not part of this prospectus supplement or the accompanying prospectus.

All reports and other documents subsequently filed by us pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act after the date of this prospectus supplement and prior to the termination of this offering shall be deemed to be incorporated by reference in this prospectus supplement and to be part hereof from the date of filing of such reports and other documents. Any statement in a document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for the purposes of this prospectus supplement to the extent that a statement contained herein modifies or supersedes such statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement.

Neither we, the selling stockholder, nor the underwriters have authorized anyone to provide any information or to make any representations other than those contained or incorporated by reference herein or in any free writing prospectus prepared by us or on our behalf to which we have referred you. Neither we, the selling stockholder, nor the underwriters take responsibility for, or provide any assurance as to the reliability of, any other information that others may give you.

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PROSPECTUS

VIANT TECHNOLOGY INC.

$100,000,000

Class A Common Stock

Preferred Stock

Debt Securities

Warrants

Purchase Contracts

Units

10,000,000 Shares

Class A Common Stock

Offered by the Selling Securityholders

We may offer and sell up to $100,000,000 in the aggregate of the securities identified above, and the selling securityholders may offer and sell up to 10,000,000 shares in the aggregate of Class A common stock identified above, including the possible resale, from time to time, of shares of our Class A common stock, par value $0.001 per share (“Class A common stock”), issuable upon the exchange of Class B units (“Class B units”) of our subsidiary, Viant Technology LLC (“Viant Technology LLC”) for an equivalent number of shares of our Class A common stock (and the automatic retirement of such selling securityholder’s shares of our Class B common stock, par value $0.001 per share (“Class B common stock”, and together with the Class A common stock, the “common stock”), as applicable, on a one-for-one basis with the number of Class B units so exchanged) in each case from time to time in one or more offerings. This prospectus provides you with a general description of the securities. We will not receive any proceeds from the sale of our Class A common stock by the selling securityholders.

Each time we or any of the selling securityholders offer and sell securities, we or such selling securityholders will provide a supplement to this prospectus that contains specific information about the offering and, if applicable, the selling securityholders, as well as the amounts, prices and terms of the securities. The supplement may also add, update or change information contained in this prospectus with respect to that offering. You should carefully read this prospectus and the applicable prospectus supplement before you invest in any of our securities.

We may offer and sell the securities described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. In addition, the selling securityholders may offer and sell shares of our Class A common stock from time to time, together or separately. If any underwriters, dealers or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections of this prospectus entitled “About this Prospectus” and “Plan of Distribution” for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE THE “RISK FACTORS” ON PAGE 7 OF THIS PROSPECTUS AND ANY SIMILAR SECTION CONTAINED IN THE APPLICABLE PROSPECTUS SUPPLEMENT CONCERNING FACTORS YOU SHOULD CONSIDER BEFORE INVESTING IN OUR SECURITIES.

Our Class A common stock is listed on the Nasdaq Global Select Market under the symbol “DSP.” On April 5, 2024 the last reported sale price of our Class A common stock on the Nasdaq Global Select Market was $11.00 per share.

Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is April 23, 2024.

TABLE OF CONTENTS


ABOUT THIS PROSPECTUS			1
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS			2
TRADEMARKS			3
WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE			4
THE COMPANY			6
RISK FACTORS			7
USE OF PROCEEDS			8
DESCRIPTION OF CAPITAL STOCK			9
DESCRIPTION OF DEBT SECURITIES			14
DESCRIPTION OF WARRANTS			22
DESCRIPTION OF PURCHASE CONTRACTS			24
DESCRIPTION OF UNITS			25
GLOBAL SECURITIES			26
SELLING SECURITYHOLDERS			30
PLAN OF DISTRIBUTION			31
LEGAL MATTERS			33
EXPERTS			33