Mock Service Worker vs Faker
Feature checklists rarely decide anything. What decides it is the pricing metric, who has to write the tests, and which limitation you can live with.
Entry price
Free and open source
Open sourceFree and open source
Open sourceWhat drives the bill
The metric that actually scales your invoice.
Free and open source. You pay in engineering time and CI minutes.
Free and open source. You pay in engineering time and CI minutes.
Free tier
Everything, self-hosted
Everything, self-hosted
Open source
MIT
MIT
Self-hostable
No-code authoring
Languages
Platforms
Fits teams
Adoption
Category standard
OSS community · since 2020
Category standard
OSS community · since 2010
Strengths
- One set of handlers reused across unit, component, E2E and local development.
- Application code is completely unaware it is being mocked — no test-only branches.
- Supports REST and GraphQL with the same model.
- Realistic, locale-aware data catches layout bugs that 'test test test' never will.
- Seedable, so generated data is reproducible when a test fails.
- Available in every major language with a similar API.
Limitations
- JavaScript ecosystem only.
- Service Worker registration adds a setup step and occasional caching confusion.
- Handlers can drift from the real API without contract verification.
- Generated data has no referential integrity or business rules — that is your job.
- Random data makes failures harder to reproduce unless you seed deliberately.
- Not a substitute for production-shaped data at realistic volume.
Best for
Front-end teams that want one mocking approach across every kind of test.
Every project that needs fixtures more realistic than placeholder strings.
All of these integrate with: Jest, Vitest.
Pricing last reviewed August 2026 and is indicative only — confirm on each vendor’s own page.