Mock Service Worker vs Snaplet Seed
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 MIT-licensed. Snaplet the company shut down in August 2024 and snaplet.dev no longer resolves; this is a community-held library, not a service.
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
Emerging
Supabase community (formerly Snaplet) · since 2021
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.
- Schema-aware generation means the data actually inserts and the app actually works.
- Deterministic seeds make failing tests reproducible.
- Good TypeScript ergonomics with Prisma and Drizzle.
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.
- Effectively unmaintained: the last npm release (0.98.0) was July 2024 and the last commit to the default branch was August 2024, though the repo is not archived.
- PostgreSQL-centric.
- TypeScript ecosystem only.
Best for
Front-end teams that want one mocking approach across every kind of test.
TypeScript teams that want each developer and CI run to start from a clean, coherent database.
Pricing last reviewed August 2026 and is indicative only — confirm on each vendor’s own page.