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Stoplight Prism
What it is
Stoplight Prism is a free, open-source command-line HTTP server that turns OpenAPI files or Postman Collections into API servers for mocking, transformations, and validation. Teams can create mock servers to try an API before its backend is built and generate dynamic random examples from an API description. Prism validates request and response data against that description. Proxy mode identifies differences between an OpenAPI document and a target API, helping with pre-production consistency checks. The project supports OpenAPI 3.1, 3.0, and 2.0, Postman Collections, and OpenAPI v3.0 callbacks that deliver payloads to URLs. Prism runs standalone or in continuous integration. Installation options include npm, standalone binaries, Docker, and Docker Compose. The listed requirement is Node.js >= 18.20.1, or >= 18.16 for Node.js 18.x. Stoplight also offers hosted Prism-powered mock servers through its Platform and Studio.
For and against
For
- Generates mocks from OpenAPI or Postman files
- Validates request and response data
- Creates dynamic random API examples
- Supports standalone and continuous-integration runs
- Docker and npm installation options
Against
- Requires Node.js versions listed by the project
- Command-line server requires technical setup
- Hosted mock servers are provided through separate Stoplight products
The verdict
Prism covers mocking, validation, transformations, callbacks, and proxy checking from API descriptions. Its open-source deployment options support local, self-hosted, and CI workflows.
Who it suits
Prism suits development teams needing API mocks, contract validation, transformations, or proxy checks. It fits workflows spanning local command-line use, self-hosting, and continuous integration.
Plans and prices
Prism Open Source
Open-source HTTP server; requires Node.js >= 18.20.1 or a standalone binary; Docker image available
Read 8 Oct 2026 · github.com
On the record
- Callbacks
- Prism supports OpenAPI v3.0 callbacks for delivering payloads to URLs.stoplight.io · read 8 Oct 2026
- Dynamic examples
- It can generate dynamic, random examples based on an API description.stoplight.io · read 8 Oct 2026
- Hosted option
- Stoplight says hosted mock servers powered by Prism are available through Stoplight Platform and Stoplight Studio.github.com · read 8 Oct 2026
- Install options
- The installation guide documents npm, standalone binaries, Docker, and Docker Compose installation options.github.com · read 8 Oct 2026
- License
- The repository identifies its license as Apache-2.0.github.com · read 8 Oct 2026
- Mock servers
- It generates mock servers from API specifications so teams can try an API before its backend is built.stoplight.io · read 8 Oct 2026
- Run modes
- Prism is an open-source command-line HTTP server that can run standalone or in continuous integration.github.com · read 8 Oct 2026
- Runtime requirement
- The README lists Node.js >= 18.20.1 as a requirement, with >= 18.16 for Node.js 18.x.github.com · read 8 Oct 2026
- Specifications
- The project README lists support for OpenAPI 3.1, 3.0, 2.0, and Postman Collections.github.com · read 8 Oct 2026
- Support
- The repository points users to Stoplight documentation and its community for help.github.com · read 8 Oct 2026
- Use cases
- The maker describes Prism as useful for parallel frontend and backend development and for checking API consistency in pre-production.stoplight.io · read 8 Oct 2026
- Validation
- Prism can validate request and response data against the API description.stoplight.io · read 8 Oct 2026
- Validation proxy
- Its proxy mode identifies discrepancies between an OpenAPI document and a target API.stoplight.io · read 8 Oct 2026
- What it does
- Prism turns OpenAPI or Postman Collection files into an HTTP API server for mocking, transformations, and validations.github.com · read 8 Oct 2026
