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

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

Opensource IDE For Exploring and Testing Api's (lightweight alternative to postman/insomnia)

Mobile Security Framework (MobSF) is an automated, all-in-one mobile application (Android/iOS/Windows) pen-testing, malware analysis and security assessment framework capable of performing static and dynamic analysis.

Hurl, run and test HTTP requests with plain text.

MeterSphere 是新一代的开源持续测试工具，让软件测试工作更简单、更高效，不再成为持续交付的瓶颈。

An interactive command-line HTTP and API testing client built on top of HTTPie featuring autocomplete, syntax highlighting, and more. https://twitter.com/httpie

Test Automation Made Simple

Unit, API & Integration Testing Agent for Developers. Generate tests, mocks/stubs for your APIs that actually work!

Newman is a command-line collection runner for Postman

Friendly and fast tool for sending HTTP requests

A payment application to demonstrate real-world usage of Cypress testing methods, patterns, and workflows.

HTTP parameter discovery suite.

Turn any OpenAPI2/3 and Postman Collection file into an API server with mocking, transformations and validations.

HttpRunner 是一款开源的 API/UI 测试框架，简单易用，功能强大，具有丰富的插件化机制和高度的可扩展能力。

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

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.

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

API Dash is a beautiful open-source cross-platform (macOS, Windows, Linux, Android & iOS) 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.

Insomnia Mockbin is the underlying backend for the API mocks capability of Insomnia. It is built and used by Kong, the author of the open-source Kong Gateway.