AnAPI can be thought of as an instruction manual for communication between multiple software apparatuses. For example, an API may be used for database communication between web applications. By extracting the implementation and relinquishing data into objects, an API simplifies programming.

Open-Source API Development Ecosystem •https://hoppscotch.io • Offline, On-Prem & Cloud • Web, Desktop & CLI • Open-Source Alternative to Postman, Insomnia

• UpdatedNov 28, 2025
• TypeScript

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

• UpdatedNov 28, 2025
• JavaScript

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

• UpdatedNov 28, 2025
• TypeScript

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

• UpdatedDec 17, 2024
• Python

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

• UpdatedNov 29, 2025
• Java

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

• UpdatedNov 29, 2025
• Vue

A single API for all your integrations.

• UpdatedNov 28, 2025
• TypeScript

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.

• UpdatedOct 10, 2025
• TypeScript

Free and open-source API Client & Interceptor.

• UpdatedNov 28, 2025
• TypeScript

Official Notion JavaScript Client

• UpdatedNov 10, 2025
• TypeScript

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

• UpdatedNov 20, 2025

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

• UpdatedMar 19, 2025

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

• UpdatedAug 24, 2025
• Go

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

• UpdatedApr 20, 2024
• JavaScript

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

• UpdatedNov 24, 2025
• PHP

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

• UpdatedNov 14, 2025
• Python

A simple API client (postman like) in your terminal

• UpdatedOct 31, 2025
• Rust

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

• UpdatedAug 29, 2025
• Ruby

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.

• UpdatedNov 20, 2025
• EJS

Offline-First Minimalistic HTTP & Socket Testing Client for the Web & Desktop

• UpdatedSep 8, 2025
• Vue