X0508 4 2023-11-14 0001701732 Altair Engineering Inc. ALTR 0001720317 Harris Teresa A C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER ROAD TROY MI 48083 1 0 Class A Common Stock 2023-11-14 4 M 0 1800 0 A 20695 D Class A Common Stock 2023-11-14 4 S 0 1800 73.157 D 18895 D Stock Option (Right to Buy) 4.52 2023-11-14 4 M 0 1800 0 D 2026-11-23 Class A Common Stock 1800 18200 D Includes 2,974 Class A Common Stock restricted stock units that are unvested. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $73.01 to $73.17 per share, inclusive. The reporting person undertakes to provide to Altair Engineering Inc., any security holder of Altair Engineering Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth herein. The options vested in 2 equal annual installments commencing November 23, 2017. This option is currently fully vested. /s/ Raoul Maitra, attorney-in-fact for Teresa Anita Harris 2023-11-16