Form S-3ASR Altair Engineering Inc.

As filed with the Securities and Exchange Commission on August 5, 2022

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

ALTAIR ENGINEERING INC.

(Exact name of registrant as specified in its charter)

Raoul Maitra

Chief Legal Officer

Altair Engineering Inc.

1820 E. Big Beaver Road

Troy, Michigan 48083

(248) 614-2400

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Kate Basmagian

Lowenstein Sandler LLP

1251 Avenue of the Americas

New York, NY 10020

(212) 262-6700

Approximate date of commencement of proposed sale to the public: From time to time after this registration statement becomes effective.

If the only securities being registered on this form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  ☐

If any of the securities being registered on this form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box.  ☒

If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.  ☒

If this form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ☐

PROSPECTUS

ALTAIR ENGINEERING INC.

2,935,564 Shares of Class A Common Stock Offered by the Selling Stockholder

This prospectus relates to the offer and sale from time to time of our Class A common stock, $0.0001 par value per share (“common stock”), by the selling stockholder named herein in amounts, at prices and on terms that will be determined at the time of any such offering. The selling stockholder may offer and sell up to 2,935,564 shares of common stock in the aggregate.

We are registering the offer and sale of shares of the common stock owned by the selling stockholder to satisfy registration rights we have granted to the selling stockholder pursuant to registration rights agreements dated as of September 27, 2021 (the “Registration Rights Agreements”). We have agreed to bear all of the expenses incurred in connection with the registration of the shares of common stock covered by this prospectus. The selling stockholder will pay or assume brokerage commissions and similar charges, if any, incurred in the sale of the shares of common stock.

We will not receive any proceeds from the sale of common stock by the selling stockholder. The common stock to which this prospectus relates may be offered and sold from time to time directly by the selling stockholder or alternatively through underwriters, broker dealers or agents. The selling stockholder will determine at what price they may sell the common stock offered by this prospectus, and such sales may be made at fixed prices, at prevailing market prices at the time of the sale, at varying prices determined at the time of sale, or at negotiated prices. For additional information on the methods of sale that may be used by the selling stockholder, see the section entitled “Plan of Distribution.”

We may amend or supplement this prospectus from time to time by filing amendments or supplements as required. You should carefully read this prospectus and any prospectus supplement or amendment before you invest in our common stock. You also should read the documents we have referred you to in the “Where You Can Find More Information” section of this prospectus for information about us and our financial statements.

Our common stock is listed on The Nasdaq Global Select Market (“Nasdaq”) under the symbol “ALTR.” On August 4, 2022, the last reported sale price of our common stock on Nasdaq was $60.88 per share.

Our principal executive office is located at 1820 E. Big Beaver Road, Troy, Michigan 48083, and our telephone number is (248) 614-2400.

Investing in our common stock involves risks. You should carefully review the risks and uncertainties described under the heading “Risk Factors” contained on page 5 herein and in the applicable prospectus supplement and under similar headings in the other documents incorporated by reference into this prospectus.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ACCURACY OR ADEQUACY OF THE DISCLOSURES IN THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

The date of this prospectus is August 5, 2022

TABLE OF CONTENTS

This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission pursuant to which the selling stockholder named herein may, from time to time, offer and sell or otherwise dispose of the common stock covered by this prospectus. You should not assume that the information contained in this prospectus is accurate on any date subsequent to the date set forth on the front cover of this prospectus or that any information we have incorporated by reference is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus is delivered or the shares of common stock are sold or otherwise disposed of on a later date. It is important for you to read and consider all information contained in this prospectus, including the documents incorporated by reference herein, in making your investment decision. You should also read and consider the information in the documents to which we have referred you under the caption “Where You Can Find More Information” in this prospectus.

We have not authorized anyone to provide any information or to make any representations other than those contained in this prospectus or in any free writing prospectuses we have prepared. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We are not, and the selling stockholder is not, making an offer to sell these securities in any jurisdiction where an offer or sale is not permitted.

This prospectus, including the information that we have incorporated by reference, contains forward-looking statements that are subject to a number of risks and uncertainties, many of which are beyond our control. Please read “Risk Factors” and “Forward-Looking Statements.”

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ABOUT THIS PROSPECTUS

This prospectus is part of a “shelf registration statement” on Form S-3 that we filed with the Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process. This prospectus provides you with a general description of the common stock the selling stockholder may offer. Each time the selling stockholder offers common stock in an underwritten offering, we will provide a prospectus supplement accompanied by this prospectus. The prospectus supplement will contain specific information about the nature of the Company, the persons offering common stock and the terms of the offering. The prospectus supplement may also add, update or change information contained in this prospectus. If there is any inconsistency between the information in this prospectus and any prospectus supplement, you should rely on the information in the prospectus supplement.

We have provided you only with the information contained in this prospectus, including information incorporated by reference in this prospectus and any applicable prospectus supplement. Neither we nor the selling stockholder have authorized anyone to provide you with different or additional information. Neither we nor the selling stockholder take any responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. Neither we nor the selling stockholder are making an offer to sell securities in any jurisdiction where the offer or sale of securities is not permitted. You should not assume that the information included in this prospectus, any applicable prospectus supplement, or the documents incorporated by reference herein is accurate as of any date other than their respective dates. Our business, financial condition, results of operations and prospects may have changed since those dates.

You should read carefully the entire prospectus and any applicable prospectus supplement, as well as the documents incorporated by reference in this prospectus, before making an investment decision.

When used in this prospectus, except where the context otherwise requires, the terms “we,” “us,” “our” and “the Company” refer to Altair Engineering Inc. and its consolidated subsidiaries.

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WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a Registration Statement on Form S-3 to register the offer and sale of the common stock covered hereby. This prospectus, which forms part of the Registration Statement, does not contain all of the information included in that Registration Statement. For further information about us and the common stock covered by this prospectus, you should refer to the Registration Statement and its exhibits. Certain information is also incorporated by reference in this prospectus as described under “Incorporation of Certain Documents by Reference.”

We are subject to the information and periodic reporting requirements of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and, in accordance therewith, file periodic reports, proxy statements and other information with the SEC. Such periodic reports, proxy statements and other information are available at the website of the SEC at http://www.sec.gov. We also furnish our stockholders with annual reports containing our financial statements audited by an independent registered public accounting firm and quarterly reports containing our unaudited financial information. We maintain a website at www.altair.com. You may access our Annual Report on Form 10-K, our Quarterly Reports on Form 10-Q, our Current Reports on Form 8-K and amendments to those reports, in each case filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act with the SEC, free of charge at our website as soon as reasonably practicable after this material is electronically filed with, or furnished to, the SEC. The reference to our website or web address does not constitute incorporation by reference of the information contained at that site.

We have not authorized anyone to provide you with any information other than that contained in this prospectus or in a document to which we expressly have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. You should assume that the information appearing in this prospectus is accurate only as of the date on the front cover of this prospectus.

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INFORMATION INCORPORATED BY REFERENCE

The SEC allows us to incorporate by reference the information we file with it. This means that we can disclose information to you by referring you to those documents. The documents that have been incorporated by reference are an important part of the prospectus, and you should review that information in order to understand the nature of any investment by you in our shares of common stock. Information that we later provide to the SEC, and that is deemed to be “filed” with the SEC, will automatically update information previously filed with the SEC, and may update or replace information in this prospectus and information previously filed with the SEC. We are incorporating by reference the documents listed below; provided, however, that we are not incorporating any documents or information deemed to have been “furnished” rather than “filed” in accordance with SEC rules unless specifically referenced below.

All documents subsequently filed by us pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act (excluding, in each case, any information deemed furnished rather than filed) shall be deemed to be incorporated by reference in this prospectus until the termination of each offering under this prospectus.

Upon request, we will provide to each person, including any beneficial owner, to whom this prospectus is delivered, a copy of any or all of the reports or documents that have been incorporated by reference in this prospectus. If you would like a copy of any of these documents, at no cost, please write or call us at:

Altair Engineering Inc.

1820 E. Big Beaver Road

Troy, Michigan 48083

(248) 614-2400

Any statement contained in a document which is incorporated by reference in this prospectus is automatically updated and superseded if information contained in the prospectus modifies or replaces this information.

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OUR COMPANY

General

We are a global leader in computational science and artificial intelligence enabling organizations across broad industry segments to drive smarter decisions in an increasingly connected world. We deliver software and cloud solutions in the areas of simulation, high-performance computing (“HPC”), data analytics, and artificial intelligence (“AI”). Our products and services help create a more sustainable future for our planet.

We refer to AI as a term to encompass sub-disciplines including data analytics, data science, data preparation, and machine learning. Altair has been incorporating AI technologies into our products for several years and we believe the evolving broad use of the term is appropriate for our product offerings, customer applications, and market opportunities.

Our simulation and AI-driven approach to innovation is powered by our broad portfolio of high-fidelity and high-performance physics solvers, our market leading technology for optimization and HPC, and our end-to-end platform for developing AI and Internet of Things (“IoT”) solutions. Our integrated suite of software optimizes design performance across multiple disciplines encompassing structures, motion, fluids, thermal, electromagnetics, system modeling, and embedded systems, while also providing AI solutions and true-to-life visualization and rendering. Our HPC solutions maximize the efficient utilization of complex compute resources and streamline the workflow management of compute-intensive tasks for applications including AI, modeling and simulation, and visualization. Our data analytics, AI, and IoT products include data preparation, data science, MLOps, orchestration, and visualization solutions that fuel engineering, scientific, and business decisions.

Corporate Information

Our principal executive offices are located at 1820 E. Big Beaver Road, Troy, Michigan 48083, and our telephone number is (248) 614-2400. We maintain a website at www.altair.com. Information contained on, or accessible through, our website is not incorporated by reference in this prospectus.

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RISK FACTORS

Investing in our common stock described herein involves risk. We urge you to carefully consider the risk factors described in our most recent Annual Report on Form 10-K and any updates in our Quarterly Reports on Form 10-Q, together with any other SEC filings that are incorporated by reference in this prospectus and, if applicable, in any prospectus supplement used in connection with an offering of our common stock, as well as the information relating to us identified herein in “Forward-Looking Statements,” before making an investment decision. Although we discuss key risks in our discussion of risk factors, new risks may emerge in the future, that may prove to be significant. Our subsequent filings with the SEC may contain amended and updated discussions of significant risks. We cannot predict future risks or estimate the extent to which they may affect our financial performance.

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FORWARD-LOOKING STATEMENTS

The information contained or incorporated by reference in this prospectus and any accompanying prospectus supplement contain statements that are not historical fact and that may be forward-looking statements within the meaning of Section 21E of the Exchange Act and Section 27A of the Securities Act of 1933, as amended (the “Securities Act”). Such statements may address, among other things, our future results of operations or financial condition, business strategy and plans and objectives of management for future operations. In some cases, you can identify forward-looking statements because they contain words such as “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “will” or “would” or the negative of these words or other similar terms or expressions.

You should not rely on forward-looking statements as predictions of future events. We have based the forward-looking statements contained in this prospectus, and any accompanying prospectus supplement, primarily on our current expectations and projections about future events and trends that we believe may affect our business, financial condition, and results of operations. The outcome of the events described in these forward-looking statements is subject to risks, uncertainties and other factors described in the section titled “Risk Factors” and elsewhere in this prospectus and any accompanying prospectus supplement. Moreover, we operate in a very competitive and rapidly changing environment. New risks and uncertainties emerge from time to time, and it is not possible for us to predict all risks and uncertainties that could have an impact on the forward-looking statements contained in this prospectus and any accompanying prospectus supplement. The results, events and circumstances reflected in the forward-looking statements may not be achieved or occur, and actual results, events or circumstances could differ materially from those described in the forward-looking statements. Please refer to the “Risk Factors” section in this prospectus, any accompanying prospectus supplement, and in Part I, Item 1A of our Annual Report on Form 10-K for the year ended December 31, 2021.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based on information available to us as of the date of this prospectus and any accompanying prospectus supplement. While we believe that information provides a reasonable basis for these statements, that information may be limited or incomplete. Our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all relevant information. These statements are inherently uncertain, and investors are cautioned not to unduly rely on these statements.

The forward-looking statements made in this prospectus and any accompanying prospectus supplement relate only to events as of the date on which the statements are made. We undertake no obligation to update any forward-looking statements made in this prospectus and any accompanying prospectus supplement to reflect events or circumstances after the date of this prospectus and any accompanying prospectus supplement or to reflect new information or the occurrence of unanticipated events, except as required by law. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments.

For further discussion of factors that could materially affect the outcome of our forward-looking statements, see “Item 1A. Risk Factors” in our Annual Report on Form 10-K, which are incorporated by reference in this prospectus, and, to the extent applicable, our Quarterly Reports on Form 10-Q and any accompanying prospectus supplement.

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USE OF PROCEEDS

We will not receive any proceeds from the sales of common stock sold by the selling stockholder.

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SELLING STOCKHOLDER

The common stock being offered by the selling stockholder are those previously issued to the selling stockholder in a private placement transaction consummated on September 27, 2021 (the “private placement”). We are registering the shares of common stock in order to permit the selling stockholder to offer the shares for resale from time to time. Except for the ownership of the shares of common stock acquired in the private placement, and the ownership of shares of common stock held prior to, or acquired subsequent to, the consummation of the private placement, the selling stockholder has not had any material relationship with us within the past three years.

The table below identifies the selling stockholder and provides other information regarding the beneficial ownership of the shares of common stock by the selling stockholder. The second column lists the number of shares of common stock beneficially owned by each selling stockholder, based on its ownership of the shares of common stock, as of August 3, 2022.

The third column lists the shares of common stock being offered by this prospectus by the selling stockholder.

In accordance with the terms of a registration rights agreement with the selling stockholder, this prospectus generally covers the resale of at least the maximum number of shares of common stock issued, as of the trading day immediately preceding the applicable date of determination and all subject to adjustment as provided in the registration right agreement. The fourth column assumes the sale of all of the shares offered by the selling stockholder pursuant to this prospectus.

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PLAN OF DISTRIBUTION

We are registering the shares of common stock previously issued in the private placement to permit the resale of these shares of common stock by the holders thereof from time to time after the date of this prospectus. We will not receive any of the proceeds from the sale by the selling stockholder of the shares of common stock. We will bear all fees and expenses incident to our obligation to register the shares of common stock.

The selling stockholder may sell all or a portion of the shares of common stock beneficially owned by them and offered hereby from time to time directly or through one or more underwriters, broker-dealers or agents. If the shares of common stock are sold through underwriters or broker-dealers, the selling stockholder will be responsible for underwriting discounts or commissions or agent’s commissions. The shares of common stock may be sold in one or more transactions at fixed prices, at prevailing market prices at the time of the sale, at varying prices determined at the time of sale, or at negotiated prices. These sales may be effected in transactions, which may involve crosses or block transactions,

If the selling stockholder effects such transactions by selling shares of common stock to or through underwriters, broker-dealers or agents, such underwriters, broker-dealers or agents may receive commissions in the form of discounts, concessions or commissions from the selling stockholder or commissions from purchasers of the shares of common stock for whom they may act as agent or to whom they may sell as principal (which discounts, concessions or commissions as to particular underwriters, broker-dealers or agents may be in excess of those customary in the types of transactions involved). In connection with sales of the shares of common stock or otherwise, the selling stockholder may enter into hedging transactions with broker-dealers, which may in turn engage in short sales of the shares of common stock in the course of hedging in positions they assume. The selling stockholder may also sell shares of common stock short and deliver shares of common stock covered by this prospectus to close out short positions and to return borrowed shares in connection with such short sales. The selling stockholder may also loan or pledge shares of common stock to broker-dealers that in turn may sell such shares.

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The selling stockholder may pledge or grant a security interest in some or all of the shares of common stock owned by them and, if they default in the performance of their secured obligations, the pledgees or secured parties may offer and sell the shares of common stock from time to time pursuant to this prospectus or any amendment to this prospectus under Rule 424(b)(3) or other applicable provision of the Securities Act of 1933, as amended, amending, if necessary, the list of selling stockholders to include the pledgee, transferee or other successors in interest as selling stockholders under this prospectus. The selling stockholder also may transfer and donate the shares of common stock in other circumstances in which case the transferees, donees, pledgees or other successors in interest will be the selling beneficial owners for purposes of this prospectus.

The selling stockholder and any broker-dealer participating in the distribution of the shares of common stock may be deemed to be “underwriters” within the meaning of the Securities Act, and any commission paid, or any discounts or concessions allowed to, any such broker-dealer may be deemed to be underwriting commissions or discounts under the Securities Act. At the time a particular offering of the shares of common stock is made, a prospectus supplement, if required, will be distributed which will set forth the aggregate amount of shares of common stock being offered and the terms of the offering, including the name or names of any broker-dealers or agents, any discounts, commissions and other terms constituting compensation from the selling stockholder and any discounts, commissions or concessions allowed or reallowed or paid to broker-dealers.

Under the securities laws of some states, the shares of common stock may be sold in such states only through registered or licensed brokers or dealers. In addition, in some states the shares of common stock may not be sold unless such shares have been registered or qualified for sale in such state or an exemption from registration or qualification is available and is complied with.

There can be no assurance that any selling stockholder will sell any or all of the shares of common stock registered pursuant to the registration statement, of which this prospectus forms a part.

The selling stockholder and any other person participating in such distribution will be subject to applicable provisions of the Exchange Act, and the rules and regulations thereunder, including, without limitation, Regulation M of the Exchange Act, which may limit the timing of purchases and sales of any of the shares of common stock by the selling stockholder and any other participating person. Regulation M may also restrict the ability of any person engaged in the distribution of the shares of common stock to engage in market- making activities with respect to the shares of common stock. All of the foregoing may affect the marketability of the shares of common stock and the ability of any person or entity to engage in market-making activities with respect to the shares of common stock.

We are required to pay all fees and expenses incident to the registration of our securities. We will indemnify the selling stockholder against liabilities, including some liabilities under the Securities Act, in accordance with the registration rights agreements, or the selling stockholder will be entitled to contribution. We may be indemnified by the selling stockholder against civil liabilities, including liabilities under the Securities Act, that may arise from any written information furnished to us by the selling stockholder specifically for use in this prospectus, in accordance with the related registration rights agreement, or we may be entitled to contribution.

Once sold under the registration statement, of which this prospectus forms a part, the shares of common stock will be freely tradable in the hands of persons other than our affiliates.

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DESCRIPTION OF COMMON STOCK

General

The following is a summary of the rights of our Class A and Class B common stock and preferred stock and certain provisions of our certificate of incorporation and bylaws. This summary does not purport to be complete and is qualified in its entirety by the provisions of our certificate of incorporation and bylaws, copies of which are filed as exhibits to our Annual Report on From 10-K for the year ended December 31, 2021 incorporated herein by reference.

Our authorized capital stock consists of 600,000,000 shares, with a par value of $0.0001 per share, of which:

Our board of directors is authorized, without stockholder approval, except with respect to Class B common stock and as required by the listing standards of the Nasdaq Global Select Market, to issue additional shares of our capital stock.

As of July 22, 2022, we had 52,201,672 shares of our Class A common stock and 27,744,574 shares of our Class B common outstanding and no shares of preferred stock outstanding. As of July 22, 2022, we had approximately 300 registered stockholders of record of our Class A common stock and four registered stockholders of record of our Class B common stock, and we believe a substantially greater number of beneficial owners who hold shares of Class A common stock through brokers, banks, or other nominees.

Class A and Class B common stock

Voting rights

Holders of our Class A common stock and Class B common stock have identical rights, provided however that, except as otherwise expressly provided in our certificate of incorporation or required by applicable law, on any matter that is submitted to a vote of our stockholders, holders of Class A common stock are entitled to one vote per share of Class A common stock and holders of Class B common stock are entitled to 10 votes per share of Class B common stock. Holders of shares of Class A common stock and Class B common stock generally vote together as a single class on all matters (including the election of directors) submitted to a vote of stockholders, unless otherwise required by Delaware law or our certificate of incorporation. Delaware law could require either holders of our Class A common stock or Class B common stock to vote separately as a single class in the following circumstances:

Under our certificate of incorporation, we may not issue any shares of Class B common stock, other than those shares issuable upon exercise of options, warrants, or similar rights to acquire Class B common stock outstanding immediately prior to the filing of the certificate of incorporation with the Secretary of State of the State of Delaware and in connection with stock dividends, unless that issuance is approved by the affirmative vote of the holders of a majority of the outstanding shares of Class A common stock and Class B common stock, each voting separately as a class.

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We have not provided for cumulative voting for the election of directors in our certificate of incorporation. Our certificate of incorporation provides for a classified board of directors consisting of three classes of

approximately equal size, each class serving staggered three-year terms. Only one class will be elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms.

No preemptive or similar rights

Our classes of common stock are not entitled to preemptive rights and are not subject to conversion (other than the Class B common stock), redemption or sinking fund provisions.

Economic rights

Except as otherwise expressly provided in our certificate of incorporation or required by applicable law, shares of Class A common stock and Class B common stock generally have the same rights and privileges and rank equally, share ratably and are identical in all respects as to all matters, including, without limitation those described below, unless otherwise stated.

Dividends and distributions

Subject to preferences that may apply to any shares of preferred stock outstanding at the time, the holders of Class A common stock and Class B common stock are entitled to share equally, identically and ratably, on a per share basis, with respect to any dividend or distribution of cash, property or shares of our capital stock paid or distributed by us, unless different treatment of the shares of each such class is approved by the affirmative vote of the holders of a majority of the outstanding shares of Class A common stock and Class B common stock, each voting separately as a class. In the event a dividend or distribution is paid in the form of shares of Class A common stock or Class B common stock or rights to acquire shares of such stock, the holders of Class A common stock shall receive Class A common stock, or rights to acquire Class A common stock, as the case may be, and the holders of Class B common stock shall receive Class B common stock, or rights to acquire Class B common stock, as the case may be.

Liquidation rights

Upon our liquidation, dissolution or winding-up, the holders of Class A common stock and Class B common stock are entitled to share equally, identically and ratably in all assets remaining after the payment of any liabilities and the liquidation preferences and any accrued or declared but unpaid dividends, if any, with respect to any outstanding preferred stock, unless different treatment of the shares of each class is approved by the affirmative vote of the holders of a majority of the outstanding shares of Class A common stock and Class B common stock, each voting separately as a class.

Change of control transactions

Upon (A) the closing of the sale, transfer or other disposition of all or substantially all of our assets, (B) the consummation of a merger, consolidation, business combination or share transfer which results in our voting securities outstanding immediately prior to the transaction (or the voting securities issued with respect to our voting securities outstanding immediately prior to the transaction) representing less than a majority of the combined voting power of our voting securities or the voting securities of the surviving or acquiring entity, (C) the closing of the transfer (whether by merger, consolidation or otherwise), in one transaction or a series of related transactions, to a person or group of affiliated persons of securities of the Company if, after closing, the transferee person or group would hold 50% or more of our outstanding voting stock (or the outstanding voting stock of the surviving or acquiring entity), (D) any voluntary or involuntary recapitalization, liquidation, dissolution or winding-up, or (E) the issuance by us of voting securities representing more than 2% of our total

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voting power to a person who held 50% or less of our total voting power immediately prior to such transaction and who following such transaction holds more than 50% of our total voting power, the holders of Class A common stock and Class B common stock will be treated equally and identically with respect to shares of Class A common stock or Class B common stock owned by them, unless different treatment of the shares of each class is approved by the affirmative vote of the holders of a majority of the outstanding shares of Class A common stock and Class B common stock, each voting separately as a class.

Subdivisions and combinations

If we subdivide or combine in any manner outstanding shares of Class A common stock or Class B common stock, the outstanding shares of the other class will be subdivided or combined in the same manner, unless different treatment of the shares of each class is approved by the affirmative vote of the holders of a majority of the outstanding shares of Class A common stock and Class B common stock, each voting as a separate class.

Conversion

Each share of our Class B common stock is automatically convertible into one share of our Class A common stock pursuant to the terms of our certificate of incorporation upon the occurrence of certain events. With respect to all beneficial owners, as defined in our certificate of incorporation, of Class B common stock, each share of Class B common stock will convert automatically into one share of Class A common stock (i) upon the date specified by affirmative vote of the holders of at least 66-2/3% of the outstanding shares of Class B common stock, (ii) if the executive holder, as defined in our certificate of incorporation, is neither (x) an executive officer of the company nor (y) a director of the company, (iii) upon the date on which the executive holder has beneficial ownership of less than 10% of the capital stock of the company, or (iv) upon the 12 year anniversary of the date of filing of our certificate of incorporation in connection with our initial public offering.

With respect to each individual beneficial owner of Class B common stock, each share of Class B common stock held by a beneficial owner will convert automatically into one share of Class A common stock (i) at any time at the option of such owner, (ii) upon any transfer, whether or not for value, except for certain transfers described in our certificate of incorporation, including, without limitation, transfers from a founder, as defined in our certificate, to another founder, or certain permitted transferees, or (iii) in the event any beneficial owner owns shares of Class B common stock constituting less than 3% of the outstanding shares of Class B common stock.

Each share of Class B common stock held by all beneficial owners of Class B common stock, except the executive holder, will convert automatically into one share of Class A common stock in the event the key holders, as defined in our certificate of incorporation, beneficially own, in the aggregate, more shares of Class B common stock than the executive holder, in which event the only holder of Class B common stock will be the executive holder.

In addition, upon the death or incapacity of a beneficial owner of Class B common stock, other than the executive holder, each share of Class B common stock held by such beneficial owner will convert automatically into one share of Class A common stock, immediately upon such death or incapacity, except, with respect to the key holders, such automatic conversion will occur on the date which is nine months after the date of such death or incapacity. Upon the death or incapacity of the executive holder, each share of Class B common stock held by all beneficial owners of Class B common stock will convert automatically into one share of Class A common stock on the date which is nine months after the date of such death or incapacity.

Preferred stock

Pursuant to our certificate of incorporation, our board of directors has the authority, without further action by the stockholders, to issue from time to time up to 45,000,000 shares of preferred stock in one or more series. Our

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board of directors may designate the rights, preferences, privileges, and restrictions of the preferred stock, including dividend rights, conversion rights, voting rights, redemption rights, liquidation preference, sinking fund terms, and the number of shares constituting any series or the designation of any series. The issuance of preferred stock could have the effect of restricting dividends on the Class A and Class B common stock, diluting the voting power of the Class A and Class B common stock, impairing the liquidation rights of the Class A and Class B common stock or delaying, deterring or preventing a change in control. Such issuance could have the effect of decreasing the market price of the Class A and Class B common stock. We currently have no plans to issue any shares of preferred stock.

Anti-takeover effects of Delaware law and our certificate of incorporation and bylaws

Our certificate of incorporation and bylaws contain provisions that could have the effect of delaying, deferring or discouraging another party from acquiring control of us. These provisions and certain provisions of Delaware law, which are summarized below, could discourage takeovers, coercive or otherwise. These provisions are also designed, in part, to encourage persons seeking to acquire control of us to negotiate first with our board of directors. We believe that the benefits of increased protection of our potential ability to negotiate with an unfriendly or unsolicited acquirer outweigh the disadvantages of discouraging a proposal to acquire us.

Dual class stock. As described above under the heading “Description of capital stock—Class A and Class B common stock—Voting rights,” our certificate of incorporation provides for a dual class common stock structure, which provides our founders and certain others with significant influence over all matters requiring stockholder approval, including the election of directors and significant corporate transactions, such as a merger or other sale of our company or its assets.

Issuance of undesignated preferred stock. As discussed above under the heading “Description of capital stock— Preferred stock,” our board of directors has the ability to designate and issue preferred stock with voting or other rights or preferences that could deter hostile takeovers or delay changes in our control or management.

Limits on ability of stockholders to act by written consent or call a special meeting. Our certificate of incorporation provides that our stockholders may not act by written consent. This limit on the ability of stockholders to act by written consent may lengthen the amount of time required to take stockholder actions. As a result, the holders of a majority of our capital stock would not be able to amend the bylaws or remove directors without holding a meeting of stockholders called in accordance with the bylaws.

In addition, our bylaws provide that special meetings of the stockholders may be called only by the chairman of our board of directors, the chief executive officer, the president (in the absence of a chief executive officer) or a majority of our board of directors. A stockholder may not call a special meeting, which may delay the ability of our stockholders to force consideration of a proposal or for holders controlling a majority of our capital stock to take any action, including the removal of directors.

Requirements for advance notification of stockholder nominations and proposals. Our bylaws establish advance notice procedures with respect to stockholder proposals and the nomination of candidates for election as directors, other than nominations made by or at the direction of our board of directors or a committee of the board of directors. These advance notice procedures may have the effect of precluding the conduct of certain business at a meeting if the proper procedures are not followed and may also discourage or deter a potential acquirer from conducting a solicitation of proxies to elect its own slate of directors or otherwise attempt to obtain control of our company.

Board classification. Our certificate of incorporation provides that our board of directors is divided into three classes, one class of which is elected each year by our stockholders. The directors in each class serve for a three-year term. Our classified board of directors may tend to discourage a third party from making a tender offer or otherwise attempting to obtain control of us because it generally makes it more difficult for stockholders to replace a majority of the directors.

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Election and removal of directors. Our certificate of incorporation and bylaws contain provisions that establish specific procedures for appointing and removing members of our board of directors. Under our certificate of incorporation and bylaws, vacancies and newly created directorships on our board of directors may be filled only by a majority of the directors then serving on our board of directors. Under our certificate of incorporation and bylaws, directors may be removed only for cause.

No cumulative voting. The Delaware General Corporation Law provides that stockholders are not entitled to the right to cumulate votes in the election of directors unless our certificate of incorporation provides otherwise. Our certificate of incorporation and bylaws do not expressly provide for cumulative voting. Without cumulative voting, a minority stockholder may not be able to gain as many seats on our board of directors as the stockholder would be able to gain if cumulative voting were permitted. The absence of cumulative voting makes it more difficult for a minority stockholder to gain a seat on our board of directors to influence our board of directors’ decision regarding a takeover.

Amendment of charter provision. Amendments of certain provisions in our certificate of incorporation would require approval by holders of at least two-thirds of our then outstanding Class A and Class B common stock, voting together as a single class.

Delaware anti-takeover statute. We are subject to the provisions of Section 203 of the Delaware General Corporation Law regulating corporate takeovers. In general, Section 203 prohibits a publicly held Delaware corporation from engaging, under certain circumstances, in a business combination with an interested stockholder for a period of three years following the date the person became an interested stockholder unless:

Generally, a business combination includes a merger, asset or stock sale, or other transaction resulting in a financial benefit to the interested stockholder. An interested stockholder is a person who, together with affiliates and associates, owns or, within three years prior to the determination of interested stockholder status, did own 15% or more of a corporation’s outstanding voting stock. We expect the existence of this provision to have an anti-takeover effect with respect to transactions our board of directors does not approve in advance. We also anticipate that Section 203 may discourage attempts that might result in a premium over the market price for the shares of Class A common stock held by stockholders.

The provisions of Delaware law and the provisions of our certificate of incorporation and bylaws could have the effect of discouraging others from attempting hostile takeovers and as a consequence, they might also inhibit temporary fluctuations in the market price of our Class A common stock that often result from actual or rumored hostile takeover attempts. These provisions might also have the effect of preventing changes in our management. It is also possible that these provisions could make it more difficult to accomplish transactions that stockholders might otherwise deem to be in their best interests.

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Choice of forum

Our bylaws designate courts in the State of Delaware as the sole and exclusive forums for certain types of actions and proceedings that may be initiated by our stockholders, which could limit our stockholders’ ability to obtain a favorable judicial forum for disputes with us or our directors, officers, or employees.

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LEGAL MATTERS

Certain legal matters in connection with the common stock offered hereby will be passed upon for us by Lowenstein Sandler LLP, New York, New York.

EXPERTS

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2021, and the effectiveness of our internal control over financial reporting as of December 31, 2021, as set forth in their reports, which are incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements and our management’s assessment of the effectiveness of internal control over financial reporting as of December 31, 2021 are incorporated by reference in reliance on Ernst & Young LLP’s reports, given on their authority as experts in accounting and auditing.

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Part II

Information Not Required in Prospectus

Item 14. Other Expenses of Issuance and Distribution.

Set forth below are the expenses expected to be incurred in connection with the issuance and distribution of the securities registered hereby and payable by us. With the exception of the SEC registration fee, the amounts set forth below are estimates.

Item 15. Indemnification of Directors and Officers.

Section 145 of the Delaware General Corporation Law, or DGCL, authorizes a corporation’s board of directors to grant, and authorizes a court to award, indemnity to officers, directors, and other corporate agents under certain circumstances and subject to certain limitations.

As permitted by Section 145 of the DGCL, our certificate of incorporation and bylaws provide that:

Section 102(b)(7) of the DGCL permits a corporation to provide in its certificate of incorporation that a director of the corporation shall not be personally liable to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, except for liability (1) for any breach of the director’s duty of loyalty to the corporation or its stockholders, (2) for acts or omissions not in good faith or which involve intentional

misconduct or a knowing violation of law, (3) for payments of unlawful dividends or unlawful stock purchases or redemptions, or (4) for any transaction from which the director derived an improper personal benefit. Our certificate of incorporation provides for such limitation of liability

Our policy is to enter into separate indemnification agreements with each of our directors and certain officers that provide the maximum indemnity allowed to directors and executive officers by Section 145 of the DGCL and also to provide for certain additional procedural protections.

These indemnification provisions and the indemnification agreements entered into between us and our directors and officers may be sufficiently broad to permit indemnification of our officers and directors for liabilities (including reimbursement of expenses incurred) arising under the Securities Act.

We have purchased and intend to maintain insurance on behalf of any person who is or was a director or officer against any loss arising from any claim asserted against him or her and incurred by him or her in any such capacity, subject to certain exclusions.

See also the undertakings set out in response to Item 17 herein.

Item 16. Exhibits and Financial Statement Schedules.

(a) Exhibits.

A list of exhibits filed with this registration statement on Form S-3 is set forth on the Exhibit Index and is incorporated herein by reference.

Item 17. Undertakings.

The undersigned registrant hereby undertakes:

(a) to file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

(i) to include any prospectus required by Section 10(a)(3) of the Securities Act of 1933;

(ii) to reflect in the prospectus any facts or events arising after the effective date of this registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in this registration statement. Notwithstanding the foregoing, any increase or decrease in the volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii) to include any material information with respect to the plan of distribution not previously disclosed in this registration statement or any material change to such information in this registration statement;

provided, however, that paragraphs (a)(i), (a)(ii) and (a)(iii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

(b) that, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof;

(c) to remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering;

(d) that, for the purpose of determining liability under the Securities Act of 1933 to any purchaser:

(i) each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(ii) each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii), or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act of 1933 shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof; provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date; and

(e) that, for the purpose of determining liability of the registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of such undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, such undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) any preliminary prospectus or prospectus of such undersigned registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) any free writing prospectus relating to the offering prepared by or on behalf of such undersigned registrant or used or referred to by such undersigned registrant;

(iii) the portion of any other free writing prospectus relating to the offering containing material information about such undersigned registrant or its securities provided by or on behalf of such undersigned registrant; and

(iv) any other communication that is an offer in the offering made by such undersigned registrant to the purchaser.

The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the provisions described under Item 15 above, or otherwise, the registrant has been advised that in the opinion of the SEC, such indemnification is against public policy as expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred

or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act of 1933 and will be governed by the final adjudication of such issue.

EXHIBIT INDEX

Exhibit Index

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the city of Troy, state of Michigan, on August 5, 2022.

POWER OF ATTORNEY

Each person whose signature appears below hereby constitutes and appoints James R. Scapa, Matthew Brown and Raoul Maitra, and each of them, as his true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution for him in any and all capacities, to sign any or all amendments or post-effective amendments to this Registration Statement, or any Registration Statement for the same offering that is to be effective upon filing pursuant to Rule 462(b) under the Securities Act of 1933, and to file the same, with exhibits hereto and other documents in connection therewith or in connection with the registration of the securities under the Securities Act of 1933, with the SEC, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary in connection with such matters and hereby ratifying and confirming all that such attorneys-in-fact and agents or any of them, or his, her or their substitute or substitutes may do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated.

Exhibit 5.1

August 5, 2022

Altair Engineering Inc.

1820 E. Big Beaver Road

Troy, Michigan 48083

Ladies and Gentlemen:

We have acted as counsel for Altair Engineering Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing of a Registration Statement on Form S-3 ASR (the “Registration Statement”), including a related prospectus filed with the Registration Statement (the “Prospectus”), with the Securities and Exchange Commission (the “Commission”) pursuant to the Securities Act of 1933, as amended (the “Securities Act”), relating to the resale or other disposition by the selling stockholder named therein (the “Selling Stockholder”) of 2,935,564 shares of Class A common stock, par value $0.0001 per share, of the Company that have been issued (the “Shares”).

In connection with this opinion, we have examined originals or copies (certified or otherwise identified to our satisfaction) of (i) the Company’s Certificate of Incorporation, (ii) the Company’s Bylaws, (iii) the Registration Statement and the Prospectus and (iv) such corporate records, agreements, documents and other instruments, and such certificates or comparable documents of public officials or of officers and representatives of the Company, as we have deemed relevant and necessary as a basis for the opinion hereinafter set forth.

In such examination, we have assumed the genuineness of all signatures, the legal capacity of all natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as certified, conformed or photostatic copies, and the authenticity of the originals of such latter documents. As to certain questions of fact material to this opinion, we have relied upon certificates or comparable documents of officers and representatives of the Company and have not sought to independently verify such facts.

Based on the foregoing, and subject to the assumptions, limitations and qualifications stated herein, we are of the opinion that the Shares to be sold by the Selling Stockholder pursuant to the Registration Statement have been duly authorized and are validly issued, fully paid and non-assessable.

The opinion expressed herein is limited to the General Corporation Law of the State of Delaware (including reported judicial decisions interpreting the General Corporation Law of the State of Delaware) and we express no opinion as to the effect on the matters covered by this letter of the laws of any other jurisdiction.

We hereby consent to the filing of this letter as an exhibit to the Registration Statement and to the reference to our firm under the caption “Legal Matters” in the Prospectus which is a part of the Registration Statement. In giving such consents, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption “Experts” in the Registration Statement (Form S-3) and related Prospectus of Altair Engineering Inc. for the registration of Class A common stock and to the incorporation by reference therein of our reports dated February 28, 2022 with respect to the consolidated financial statements of Altair Engineering Inc., and the effectiveness of internal control over financial reporting of Altair Engineering Inc., included in its Annual Report (Form 10-K) for the year ended December 31, 2021, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Detroit, Michigan

August 5, 2022

Exhibit 107

Calculation of Filing Fee Table

Form S-3

(Form Type)

Altair Engineering Inc.

(Exact Name of Registrant as Specified in its Charter)