Prism vs Mockoon

Free and open source

From $9 per user/month (indicative, Cloud)

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

Free locally; the paid cloud tier adds hosted mocks and team sync.

Everything, self-hosted

The desktop app and CLI are free and open source.

Established

Stoplight (SmartBear) · since 2017

Widely used

Mockoon · since 2017

• The mock is generated from the spec, so it cannot silently diverge from the contract.
• Validation proxy mode checks that a real implementation matches its own spec.
• Zero configuration beyond having an OpenAPI file.

• Genuinely a minute from download to a working mock API.
• Dynamic templating with faker-style helpers produces realistic responses.
• Proxy mode mocks only the routes you need and passes the rest through.

• Useless without an accurate OpenAPI document.
• Limited stateful behaviour — it is spec-driven, not scenario-driven.
• Generated example data is uninteresting unless examples are in the spec.

• Desktop-first; sharing mocks across a team needs the paid cloud or a committed config file.
• HTTP only.
• Less suited to complex stateful behaviour than WireMock.

Design-first API teams who want mocks that are provably in sync with the contract.

Front-end developers unblocking themselves while a backend is still being built.