X0508 4 2024-09-30 0001666134 BLACKLINE, INC. BL 0001688366 Partin Mark 21300 VICTORY BLVD., 12TH FLOOR WOODLAND HILLS CA 91367 1 CHIEF FINANCIAL OFFICER 1 Common Stock 2024-09-30 4 M 0 39643 14.00 A 266487 D Common Stock 2024-09-30 4 M 0 45665 14.00 A 312152 D Common Stock 2024-09-30 4 S 0 14423 54.20 D 297729 D Common Stock 2024-09-30 4 S 0 68025 54.93 D 229704 D Common Stock 2024-09-30 4 S 0 2860 55.78 D 226844 D Stock Option (Right to Buy) 14.00 2024-09-30 4 M 0 39643 0 D 2025-03-29 Common Stock 39643 0 D Stock Option (Right to Buy) 14.00 2024-09-30 4 M 0 45665 0 D 2026-10-16 Common Stock 45665 0 D The 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 $53.50 to $54.47 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 $54.50 to $55.40 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 $55.51 to $56.14 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 options became exercisable based on the following vesting schedule: The shares subject to the option vested in 4 equal, annual installments beginning on the one-year anniversary of the grant date, subject to the reporting person's continued service through each applicable vesting date. /s/ Karole Morgan-Prager, Attorney-in-Fact 2024-10-01