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10 Most Popular Open-Source API & Mock Server Solutions

The most-starred open-source API clients, mock servers and contract tools — Prism, WireMock, Mockoon, MSW and more — with GitHub links and star counts.

By The DevFixPro Editorial Team · independent editorial research project

Star counts retrieved from the GitHub API on 2026-08-17. Open-source projects grow daily, so treat the numbers as a snapshot — always check the linked repository for the latest figures, license, and activity.

Front-end and integration work speeds up with a mock API. The 10 open-source API and mock-server solutions below are ranked by GitHub stars (fetched 2026-08-17) — mock servers, service workers and API clients. Each links to its repository.

Use Mock Service Worker or Mirage for in-browser mocking, Prism/WireMock/Mockoon for stand-alone servers, and Bruno/Hoppscotch/Swagger UI for hands-on API testing.

  1. 1Mockoon on GitHub
    Mockoon★ 8,367
    By Mockoon Team

    Friendly, desktop-first tool to mock APIs in seconds.

    View on GitHub →
  2. 2Prism on GitHub
    Prism★ 5,007
    By Stoplight

    Turn OpenAPI specs into live mock servers and validators.

    View on GitHub →
  3. 3WireMock on GitHub
    WireMock★ 7,335
    By WireMock Community

    Flexible HTTP mock server for stubbing and verification.

    View on GitHub →
  4. 4JSON Server on GitHub
    JSON Server★ 75,692
    By typicode

    Instant full fake REST API from a JSON file.

    View on GitHub →
  5. 5Mock Service Worker on GitHub
    Mock Service Worker★ 18,143
    By MSW Team

    API mocking library using Service Workers in the browser and Node.

    View on GitHub →
  6. 6Mirage JS on GitHub
    Mirage JS★ 5,530
    By Mirage JS

    Build realistic APIs for front-end prototypes in the browser.

    View on GitHub →
  7. 7Hoppscotch on GitHub
    Hoppscotch★ 80,047
    By Hoppscotch

    Lightweight, web-based API client and testing tool.

    View on GitHub →
  8. 8Bruno on GitHub
    Bruno★ 46,375
    By usebruno

    Offline-first, Git-friendly open-source API client.

    View on GitHub →
  9. 9Kong on GitHub
    Kong★ 43,990
    By Kong Inc.

    Open-source API gateway and microservice management layer.

    View on GitHub →
  10. 10Swagger UI on GitHub
    Swagger UI★ 28,974
    By SmartBear

    Render interactive OpenAPI documentation in the browser.

    View on GitHub →

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