X0407 4 2023-04-03 0 0001666134 BLACKLINE, INC. BL 0001688366 Partin Mark 21300 VICTORY BLVD 12TH FLOOR WOODLAND HILLS CA 91367 0 1 0 0 Chief Financial Officer 0 Common Stock 2023-04-03 4 M 0 10000 14.00 A 209479 D Common Stock 2023-04-03 4 S 0 8437 64.4921 D 201042 D Common Stock 2023-04-03 4 S 0 1548 65.5457 D 199494 D Common Stock 2023-04-03 4 S 0 15 66.3043 D 199479 D Stock Option (Right to Buy) 14.00 2023-04-03 4 M 0 10000 0.00 D 2025-03-29 Common Stock 10000 97676 D The sale transaction reported on this Form 4 was effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on December 9, 2022. The sale price represents the weighted-average price of shares sold ranging from $64.06 to $64.78 per share. 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 $65.025 to $66.04 per share. 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 $66.29 to $66.505 per share. 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 2023-04-03