144 0001762863 XXXXXXXX LIVE 0001701732 Altair Engineering Inc. 001-38263 1820 E. BIG BEAVER ROAD Troy MI 48083 248-614-2400 Messano Amy Officer Class A Common Stock Morgan Stanley Smith Barney LLC

Harborside 2 200 Hudson Street, Suite 501 Jersey City NJ 07311

153 12910.02 56948286 05/08/2024 NASDAQ Class A Common Stock 05/07/2024 Class A Common Stock Restricted Stock Unit Vesting Issuer N 523 05/07/2024 N/A N Amy Messano

1820 E. Big Beaver Rd. Troy MI 48083

Class A Common Stock 02/28/2024 236 19741.64 Amy Messano

1820 E. Big Beaver Rd. Troy MI 48083

Class A Common Stock 03/04/2024 291 24828.12 Amy Messano

1820 E. Big Beaver Rd. Troy MI 48083

Class A Common Stock 03/13/2024 112 9145.45 Represents registered Class A common stock sold pursuant to the Issuer's 2017 Equity Incentive Plan for sell-to-cover transactions for tax withholding obligations resulting from the vesting of Class A common stock restricted stock units. Such sale was previously reported on a Form 4. 05/20/2024 Amy Messano