[opensourcedex]

best-of ranking · updated nightly

Best Open Source API Development & Testing Tools

Ranked by GitHub stars — actual adoption, not editorial taste. All 10 are free, open source and self-hostable; license and last activity on every entry.

  1. 1
    fastapi ★ 102K

    FastAPI framework, high performance, easy to learn, fast to code, ready for production

    MIT Python pushed 2026-09-14 details →
  2. 2
    Hoppscotch ★ 80K

    Sleek, intuitive API development and testing platform

    MIT TypeScript pushed 2026-09-16 details →
  3. 3
    Bruno ★ 47K

    Lightweight, fast, and open-source API client for developers

    MIT JavaScript pushed 2026-09-17 details →
  4. 4
    Insomnia ★ 40K

    Powerful API development and testing made effortless

    Apache-2.0 TypeScript pushed 2026-09-17 details →
  5. 5
    one-api ★ 37K

    LLM API 管理 & 分发系统，支持 OpenAI、Azure、Anthropic Claude、Google Gemini、DeepSeek、字节豆包、ChatGLM、文心一言、讯飞星火、通义千问、360 智脑、腾讯混元等主流模型，统一 API 适配，可用于 key 管理与二次分发。单可执行文件，提供 Docke

    MIT JavaScript pushed 2026-01-09 details →
  6. 6
    OpenAPI-Specification ★ 31K

    The OpenAPI Specification Repository

    Apache-2.0 Markdown pushed 2026-09-11 details →
  7. 7
    openapi-generator ★ 27K

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

    Apache-2.0 Java pushed 2026-09-17 details →
  8. 8
    redoc ★ 26K

    📘 OpenAPI/Swagger-generated API Reference Documentation

    MIT TypeScript pushed 2026-09-16 details →
  9. 9
    SafeLine ★ 23K

    SafeLine is a self-hosted WAF(Web Application Firewall) / reverse proxy to protect your web apps from attacks and exploits.

    GPL-3.0 Go pushed 2026-09-10 details →
  10. 10
    Mobile-Security-Framework-MobSF ★ 22K

    Mobile Security Framework (MobSF) is an automated, all-in-one mobile application (Android/iOS/Windows) pen-testing, malware analysis and security assessment fra

    GPL-3.0 JavaScript pushed 2026-09-09 details →
method stars desc · snapshot from github api refresh nightly related AI Assisted Coding, Build & Deployment, Website Builders, Terminals, IDEs & Code Editors, Testing & Quality Assurance

Related best-of lists

best AI Assisted Coding →best Build & Deployment →best Website Builders →best Terminals →best IDEs & Code Editors →best Testing & Quality Assurance →

last updated nightly · ranking method: github stars, live-tracked

Looking for a replacement for one specific commercial product? Browse alternatives by tool →

Frequently asked questions

What is the best open source API Development & Testing tool in 2026?

fastapi leads the ranking with 102,402 GitHub stars, ahead of Hoppscotch. Rankings use live GitHub star counts, refreshed nightly.

How is this list of API Development & Testing tools ranked?

By GitHub stars — a proxy for adoption and community size. Each entry also shows its licence, primary language and last commit date, so you can judge maintenance activity rather than trusting the ranking alone.

Are the best API Development & Testing tools free?

Every project on this list is open source and free to self-host. Some also offer paid managed hosting, but the software itself carries no licence fee.