X0508 4 2024-10-18 0001666134 BLACKLINE, INC. BL 0001183627 Morgan-Prager Karole 21300 VICTORY BLVD., 12TH FLOOR WOODLAND HILLS CA 91367 1 CHIEF LEGAL AND ADMINISTRATIVE 1 Common Stock 2024-10-18 4 M 0 3649 14.00 A 117514 D Common Stock 2024-10-18 4 M 0 3649 14.00 A 121163 D Common Stock 2024-10-18 4 M 0 19781 14.00 A 140944 D Common Stock 2024-10-18 4 S 0 27079 60.06 D 113865 D Stock Option (Right to Buy) 14.00 2024-10-18 4 M 0 3649 0 D 2026-10-16 Common Stock 3649 73611 D Stock Option (Right to Buy) 14.00 2024-10-18 4 M 0 3649 0 D 2026-10-16 Common Stock 3649 69962 D Stock Option (Right to Buy) 14.00 2024-10-18 4 M 0 19781 0 D 2026-10-16 Common Stock 19781 50181 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 8, 2024. The sale price represents the weighted average price of shares sold ranging from $60.00 to $60.215 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 2024-10-21