Company: BL
Filing Date: 2025-02-21
Form Type: S-8
Source: 0001193125-25-032083
Chunk: 0

Company: BLACKLINE, INC.
Filing Date: 2025-02-21
Form: S-8
Chunk 0
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As filed with the Securities and Exchange Commission on February 21, 2025 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-8 REGISTRATION STATEMENT Under The Securities Act of 1933 BlackLine, Inc. (Exact name of Registrant as specified in its charter)

| Delaware                        |     | 46-3354276            |
| (State or other jurisdiction of 
 incorporation or organization)  |     | -I.R.S. Employer      
 Identification Number |

21300 Victory Boulevard, 12th Floor Woodland Hills, CA 91367 (818) 223-9008 (Address of principal executive offices, including zip code) 2016 Equity Incentive Plan (Full title of the plan) Therese Tucker, Co-ChiefExecutive Officer Owen Ryan, Co-ChiefExecutive Officer BlackLine, Inc. 21300 Victory Boulevard 12th Floor Woodland Hills, CA 91367 (818) 223-9008 (Name, address and telephone number, including area code, of agent for service) Copies to:

| Katharine A. Martin, Esq.              |     | Karole Morgan-Prager, Esq.             |
| Allison B. Spinner, Esq.               |     | Chief Legal and Administrative Officer |
| Lisa L. Stimmell, Esq.                 |     | BlackLine, Inc.                        |
| Wilson Sonsini Goodrich & Rosati, P.C. |     | 21300 Victory Boulevard, 12th Floor    |
| 650 Page Mill Road                     |     | Woodland Hills, CA 91367               |
| Palo Alto, CA 94304                    |     | (818) 223-9008                         |
| (650) 493-9300                         |     |                                        |

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-acceleratedfiler, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2of the Exchange Act.

| Large accelerated filer |     | ☒ |     | Accelerated filer         |     | ☐ |
| Non-accelerated filer   |     | ☐ |     | Smaller reporting company |