API Development & Testing Tools

3 open source API development and testing tools you can self-host. Compare Postman, Insomnia, and Hoppscotch alternatives by features and license. Updated Sept 2026.

Scalar

11,821459

Featured

Scalar is an offline-first, open-source API client designed for modern developers working with OpenAPI/Swagger.

8/28/2025459 contributors

Insomnia

35,3922,010

An open-source, cross-platform API client that enables debugging, designing, testing, and mocking APIs across multiple protocols and formats.

1/13/20252010 contributors

Hoppscotch

66,3354,615

An open-source API development ecosystem that helps developers create, test, and manage API requests efficiently with a user-friendly interface and powerful features.

12/23/20244615 contributors