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.

Mock Service WorkerFaker

Entry price

Free and open source

Open source

Free and open source

Open source

What drives the bill

The metric that actually scales your invoice.

Free and open source. You pay in engineering time and CI minutes.

Free tier

Everything, self-hosted

Open source

MIT

Self-hostable

No-code authoring

Languages

JavaScriptTypeScript

JavaScriptTypeScriptPythonJavaRubyPHPGo

Platforms

WebAPI

Fits teams

Solo / side projectStartupScale-up / mid-marketEnterprise

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

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.