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 (open-source alternative to Postman, Insomnia)

• UpdatedJul 18, 2025
• TypeScript

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

• UpdatedJul 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

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

• UpdatedJul 18, 2025
• JavaScript

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

• UpdatedJul 18, 2025
• Java

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

• UpdatedJul 18, 2025
• Vue

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.

• UpdatedJul 7, 2025
• TypeScript

A single API for all your integrations.

• UpdatedJul 18, 2025
• TypeScript

Official Notion JavaScript Client

• UpdatedJul 10, 2025
• TypeScript

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

• UpdatedAug 21, 2024

Local-first Developer Tool to Build, Test, Intercept & Mock API Requests. Requestly is a combination of REST API Client and HTTP Interceptor. It is simple, beautiful and powerful alternative to Postman, Insomnia, Bruno and Charles Proxy.

• UpdatedJul 18, 2025
• TypeScript

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

• UpdatedMar 19, 2025

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

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

• UpdatedMay 2, 2025
• Go

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

• UpdatedJul 14, 2025
• PHP

OpenAI API + Ruby! 🤖❤️ Now with Responses API + DeepSeek!

• UpdatedJul 16, 2025
• Ruby

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

• UpdatedJun 19, 2025
• Python

A simple API client (postman like) in your terminal

• UpdatedJul 10, 2025
• Rust

Given a web API, Generate client libraries in node, php, python, ruby

• UpdatedDec 19, 2019
• Go

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

• UpdatedJul 30, 2024
• TypeScript