X0508 4 2024-06-04 0001666134 BLACKLINE, INC. BL 0001688366 Partin Mark 21300 VICTORY BLVD., 12TH FLOOR WOODLAND HILLS CA 91367 1 CHIEF FINANCIAL OFFICER 1 Common Stock 2024-06-04 4 M 0 50000 14.00 A 279341 D Common Stock 2024-06-04 4 S 0 44029 47.299 D 235312 D Common Stock 2024-06-04 4 S 0 5971 47.994 D 229341 D Stock Option (Right to Buy) 14.00 2024-06-04 4 M 0 50000 0 D 2025-03-29 Common Stock 50000 42676 D The sale transaction reported on this Form 4 was effectuated pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 6, 2024. The sale price represents the weighted average price of shares sold ranging from $46.76 to $47.728 per share, and is rounded to the nearest tenth of a cent. Upon request by the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4. The sale price represents the weighted average price of shares sold ranging from $47.76 to $48.17 per share, and is rounded to the nearest tenth of a cent. Upon request by the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4. The option is fully vested and immediately exercisable. /s/ Karole Morgan-Prager, Attorney-in-Fact 2024-06-06