Developer Tools

msw

Last updated 2026-06-06 · benchmark checked 2026-08-09 · unchanged since 2026-07-30 — deterministic & reproducible

Mock Service Worker is an API mocking library for browser and Node.js.

Is msw production-ready?

Legit.Show scores msw 68 out of 100 — the simple average of its 7 measured frames. Legit.Show ran its deterministic 7-Frame production-readiness benchmark on msw (public-surface assessment), measured from the public surface with no LLM in the scoring path. Its strongest frame is Reliability; its weakest is Privacy. Every frame it averages is published with its evidence on the Legit.Show listing.

The 7 Frames

• Performance — 64/100
• Accessibility — 67/100
• Security — 45/100
• Privacy — 25/100
• Reliability — 100/100
• Standards — 100/100
• Discoverability — 75/100

What we measured

• Security headers present: HSTS.
• No Content-Security-Policy.
• Served over HTTPS with a valid certificate.
• Real Lighthouse performance run — 182 ms to first byte.
• Returns a proper 404 for unknown routes.
• 3 of 3 sampled routes reachable.
• No privacy policy found.
• Sets cookies / loads scripts with no consent prompt.

Who built it

Artem Zakharchenko (@kettanaito) · product account @ApiMocking

Who it's for

JavaScript developers · QA engineers · Frontend teams · Test automation specialists

Visit msw → · Alternatives to msw → · How this was measured →