Assembly Line

API clients and testing tools in 2026

1 commercial product, ranked by how many people read about each, or about its maker, on Wikipedia's mobile site. Of those with an article of their own, Postman has the most readers, about 1k a month. 30 open-source projects, ranked by GitHub stars and how recently each was worked on. Hoppscotch leads with 81k stars, ahead of Bruno. 24 had code pushed in the last three months. Most common licenses: MIT (22), Apache-2.0 (5) and BSD-3-Clause (2).

Commercial API clients and testing tools

  1. 1
    Postman Postman, Inc.

    Go faster from development to production with higher accuracy and fewer tokens.

    Developer tool Production-ready A team wants shared API collections, tests and documentation in one widely known tool.

    1k readers a month Commercial

Open-source API clients and testing tools

Complete systems you can adopt 1

  1. 1
    RWKV-Runner josStorer

    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.

    Complete system Usable You want to run RWKV models on your own PC and use them from ChatGPT-style clients.

    ★ 6.5k MIT TypeScript Active, pushed today

Building blocks for your own system 2

  1. 1
    Notion-sdk-js makenotion

    Official Notion JavaScript Client

    Building block Production-ready You build an integration or automation against Notion in JavaScript.

    ★ 5.7k MIT TypeScript Active, pushed today
  2. 2
    Nba_api swar

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

    Building block Usable You analyse basketball statistics in Python.

    ★ 3.9k MIT Python Active, pushed 5 days ago

Developer tools 7

  1. 1
    Hoppscotch hoppscotch

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

    Developer tool Production-ready Your team wants a Postman-like client that it can self-host or use in the browser.

    ★ 81k MIT TypeScript Active, pushed 2 days ago
  2. 2
    Bruno usebruno

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

    Developer tool Production-ready You want Postman-style testing without cloud sync, keeping collections in your repository.

    ★ 48k MIT JavaScript Active, pushed today
  3. 3
    Insomnia Kong

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

    Developer tool Production-ready You need an API client with API design features and work in the Kong ecosystem.

    ★ 40k Apache-2.0 TypeScript Active, pushed today
  4. 4
    Yaak mountain-loop

    The most intuitive desktop API client. Organize and execute REST, GraphQL, WebSockets, Server Sent Events, and gRPC 🦬

    Developer tool Production-ready You want a fast, local Postman alternative without an account.

    ★ 19k MIT TypeScript Active, pushed yesterday
  5. 5
    Scalar scalar

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

    Developer tool Production-ready You publish an OpenAPI spec and want better-looking docs than Swagger UI with try-it-out requests.

    ★ 16k MIT TypeScript Active, pushed today
  6. 6
    Hey API hey-api

    👨‍🚀 Turn API specifications into production-ready SDKs, validators, mocks, and more. 20+ plugins. Millions of weekly npm downloads. Used by Vercel, OpenCode, PayPal, AWS, Autodesk, and many more.

    Developer tool Production-ready Your TypeScript front end or service consumes an OpenAPI-described API and you want generated, typed clients.

    ★ 5.6k MIT TypeScript Active, pushed 2 days ago
  7. 7
    ATAC Julien-cpsn

    A simple API client (postman like) in your terminal

    Developer tool Usable You live in the terminal and want a Postman-style client there.

    ★ 3.7k MIT Rust Active, pushed 14 days ago

All 30 open-source API client projects

Looking for an alternative to

PostmanInsomnia Enterprise

Open-source licenses

  • Permissive: 29. Use it anywhere, including in closed products. You keep the copyright notice; Apache-2.0 also grants patent rights.
  • Network copyleft: 1. Like GPL, and running a changed version as a web service counts as distributing it, so its users get the source too.

Languages

TypeScript 14, Python 5, Go 3, PHP 3, JavaScript 1, Rust 1, Dart 1, C++ 1 and Ruby 1.

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