Mock Service Worker vs Hoverfly
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
Apache-2.0
Self-hostable
No-code authoring
Languages
Platforms
Fits teams
Adoption
Category standard
OSS community · since 2020
Emerging
SpectoLabs · since 2016
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.
- Capture mode produces a realistic simulation from live traffic with no authoring.
- Latency injection makes it useful for performance and resilience testing too.
- Small footprint — a single Go binary.
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.
- Smaller community and slower development than WireMock.
- Proxy configuration in complex networks takes effort.
- Captured simulations need periodic refresh.
Best for
Front-end teams that want one mocking approach across every kind of test.
Teams needing lightweight service virtualisation against real recorded traffic.
Pricing last reviewed August 2026 and is indicative only — confirm on each vendor’s own page.