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

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

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

🥧 HTTPie CLI — modern, user-friendly command-line HTTP client for the API era. JSON support, colors, sessions, downloads, plugins & more.

OpenAPI Generator allows generation of API client libraries (SDK generation), server stubs, documentation and configuration automatically given an OpenAPI Spec (v2, v3)

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

A RWKV management and startup tool, full automation, only 8MB. And provides an interface compatible with the OpenAI API. RWKV is a large language model that is fully open source and available for commercial use.

A single API for all your integrations.

Official Notion JavaScript Client

Free and open-source API Client & Interceptor.

📚 A collection of useful resources for building RESTful HTTP+JSON APIs.

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

Insomnium is a fast local API testing tool that is privacy-focused and 100% local. For testing GraphQL, REST, WebSockets and gRPC. This is a fork of Kong/insomnia

The power of curl, the ease of use of httpie.

PHP Curl Class makes it easy to send HTTP requests and integrate with web APIs

OpenAI API + Ruby! 🤖❤️ GPT-5 & Realtime WebRTC compatible!

An API Client package to access the APIs for NBA.com

A simple API client (postman like) in your terminal

Developer-first OpenSource API DevTool, Postman/Insomnia alternative.

DummyJSON.com provides different types of REST Endpoints filled with JSON data which you can use in developing the frontend with your favorite framework and library without worrying about writing a backend.