X0609 4 2026-08-24 0001666134 BLACKLINE, INC. BL 0001688365 Tucker Therese false 21300 VICTORY BLVD., 12TH FLOOR WOODLAND HILLS CA 91367 1 0 Common Stock 2026-08-24 4 M 0 70000 14.00 A 424997 D Common Stock 2026-08-24 4 M 0 26560 14.00 A 451557 D Common Stock 2026-08-24 4 S 0 70000 31.957 D 381557 D Common Stock 100178 I Brian and Therese Tucker Charitable Remainder Trust Common Stock 1509881 I Brian and Therese Tucker Living Trust Common Stock 54074 I Claire Seimetz 2015 Trust Common Stock 577200 I Isaac Tucker 2012 Irrevocable Trust Common Stock 577200 I Roseanna Tucker 2012 Irrevocable Trust Common Stock 52444 I Tucker Family CLAT Common Stock 874128 I Tucker Legacy Trust Common Stock 129897 I Tucker Legacy Trust II Common Stock 250916 I Tucker Seimetz Safety Net Grat Stock Option (Right to Buy) 14.00 2026-08-24 4 M 0 70000 0 D 2026-10-16 Common Stock 70000 26560 D Stock Option (Right to Buy) 14.00 2026-08-24 4 M 0 26560 0 D 2026-10-16 Common Stock 26560 0 D The sale price represents the weighted-average price of shares sold ranging from $31.78 to $32.14 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 2026-08-26