X0508 4 2024-03-13 0001701732 Altair Engineering Inc. ALTR 0001720314 Scapa James Ralph C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER RD. TROY MI 48083 1 1 1 Chief Executive Officer 0 Class A Common Stock 2024-03-13 4 S 0 1686 81.6594 D 98605 D Class A Common Stock 2024-03-13 4 S 0 93 81.66 D 1202 I By wife Shares sold to satisfy the tax withholding obligation in connection with the vesting of Class A Common Stock restricted stock units. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $81.19 to $81.66 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. Includes 59,042 Class A Common Stock restricted stock units that are unvested. Includes 41 Class A Common Stock restricted stock units that are unvested. /s/ Raoul Maitra, attorney-in-fact for James R. Scapa 2024-03-14