Best Open Source API Development & Testing Tools in 2026

Tools for designing, testing, documenting, and managing APIs used by developers and engineering teams.

The most popular pick this year is Hoppscotch with 79,162 GitHub stars, but all 6 options below are worth considering depending on your needs.

6 open source api development & testing tools — ranked by GitHub stars. Browse all

Hoppscotch

Open source API development ecosystem - https://hoppscotch.io (open-source alternative to Postman, Insomnia)

Alternative to:

Postman

Bruno

Opensource IDE For Exploring and Testing API's (lightweight alternative to Postman/Insomnia)

Alternative to:

Postman

Insomnia

The open-source, cross-platform API client for GraphQL, REST, WebSockets, SSE and gRPC. With Cloud, Local and Git storage.

Alternative to:

Postman

HTTPie

🚀 HTTPie Desktop — cross-platform API testing client for humans. Painlessly test REST, GraphQL, and HTTP APIs.

Alternative to:

Postman

Yaak

The most intuitive desktop API client. Organize and execute REST, GraphQL, WebSockets, Server Sent Events, and gRPC 🦬

Alternative to:

Postman

Scalar

Scalar is an open-source API platform:　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　🌐 Modern Rest API Client　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　📖 Beautiful API References　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　✨ 1st-Class OpenAPI/Swagger Support

Alternative to:

Postman

How we rank these tools

Tools are ranked by GitHub stars as a proxy for community adoption and trust. Stars reflect how many developers found a project valuable enough to bookmark — a reasonable signal for quality in the open source world. We only list tools that are actively maintained and open source.

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