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Stoplight Prism

github.com

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What it is

Stoplight Prism is a free, open-source command-line HTTP server for turning OpenAPI documents or Postman Collections into working API endpoints. It can create mock servers so frontend and backend teams can exercise an API before the backend exists. Prism validates request and response data against the API description, generates dynamic random examples, and supports OpenAPI v3.0 callbacks that send payloads to URLs. Its proxy mode compares a target API with an OpenAPI document and identifies discrepancies, helping with pre-production consistency checks. The project lists OpenAPI 3.1, 3.0, and 2.0 support alongside Postman Collections. Prism runs standalone or in continuous integration, with installation through npm, standalone binaries, Docker, or Docker Compose. The listed runtime requirement is Node.js >= 18.20.1, or >= 18.16 for Node.js 18.x. Hosted Prism-powered mock servers are available through Stoplight Platform and Stoplight Studio. The project uses the Apache-2.0 license.

Spec sheet

What it does
Prism turns OpenAPI or Postman Collection files into an HTTP API server for mocking, transformations, and validations.Read 8 Oct 2026 · github.com
Support
The repository points users to Stoplight documentation and its community for help.Read 8 Oct 2026 · github.com
License
The repository identifies its license as Apache-2.0.Read 8 Oct 2026 · github.com
Callbacks
Prism supports OpenAPI v3.0 callbacks for delivering payloads to URLs.Read 8 Oct 2026 · stoplight.io
Dynamic examples
It can generate dynamic, random examples based on an API description.Read 8 Oct 2026 · stoplight.io
Hosted option
Stoplight says hosted mock servers powered by Prism are available through Stoplight Platform and Stoplight Studio.Read 8 Oct 2026 · github.com
Install options
The installation guide documents npm, standalone binaries, Docker, and Docker Compose installation options.Read 8 Oct 2026 · github.com
Mock servers
It generates mock servers from API specifications so teams can try an API before its backend is built.Read 8 Oct 2026 · stoplight.io
Run modes
Prism is an open-source command-line HTTP server that can run standalone or in continuous integration.Read 8 Oct 2026 · github.com
Runtime requirement
The README lists Node.js >= 18.20.1 as a requirement, with >= 18.16 for Node.js 18.x.Read 8 Oct 2026 · github.com
Specifications
The project README lists support for OpenAPI 3.1, 3.0, 2.0, and Postman Collections.Read 8 Oct 2026 · github.com
Use cases
The maker describes Prism as useful for parallel frontend and backend development and for checking API consistency in pre-production.Read 8 Oct 2026 · stoplight.io
Validation
Prism can validate request and response data against the API description.Read 8 Oct 2026 · stoplight.io
Validation proxy
Its proxy mode identifies discrepancies between an OpenAPI document and a target API.Read 8 Oct 2026 · stoplight.io

Plans and prices

Prism Open Source Free Open-source HTTP server; requires Node.js >= 18.20.1 or a standalone binary; Docker image available Read 8 Oct 2026 · github.com

Every Stoplight Prism plan and price →

Strong points and limits

Strong points

  • Free open-source HTTP server
  • Mocks APIs before backends are built
  • Validates requests and responses
  • Supports OpenAPI and Postman Collections
  • Runs standalone or in CI

Limits

  • Requires Node.js version 18.20.1 or newer
  • Proxy comparisons require an OpenAPI document
  • Hosted servers use Stoplight Platform or Studio

Who it suits

It suits teams developing frontend and backend work in parallel, validating API contracts, or virtualizing services before production. It also fits CI workflows needing an API server from an existing specification.

Verdict

Prism combines mocking, validation, transformations, dynamic examples, and proxy checks around documented APIs. Its free command-line and deployment options suit specification-driven development and CI.

Where Specifiction places it

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