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

• UpdatedDec 16, 2025
• TypeScript

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

• UpdatedDec 17, 2025
• JavaScript

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

• UpdatedDec 17, 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)

• UpdatedDec 17, 2025
• Java

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

• UpdatedDec 17, 2025
• TypeScript

A single API for all your integrations.

• UpdatedDec 17, 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.

• UpdatedDec 10, 2025
• TypeScript

Free and open-source API Client & Interceptor.

• UpdatedDec 17, 2025
• TypeScript

Official Notion JavaScript Client

• UpdatedDec 16, 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.

• UpdatedDec 7, 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

• UpdatedDec 12, 2025
• PHP

A simple API client (postman like) in your terminal

• UpdatedOct 31, 2025
• Rust

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

• UpdatedDec 15, 2025
• Python

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.

• UpdatedDec 10, 2025
• EJS

API Dash is a beautiful AI-powered open-source cross-platform (Desktop & Mobile) API Client built using Flutter which can help you easily create & customize your HTTP & GraphQL API requests, visually inspect responses and generate API integration code. A lightweight alternative to postman/insomnia.

• UpdatedDec 14, 2025
• Dart