Awesome-API-Testing-Tools

Top API Testing Tools Ecosystem

Curated List of SaaS Products & Open-Source GitHub Projects
Focused on API Development, Testing & Debugging Tools
Last updated: March 2026

This repository tracks notable SaaS platforms and open-source projects for API testing, development, and debugging. These tools help developers design, test, debug, mock, and monitor APIs with features like request building, response visualization, collections, environments, automation, and collaboration.

Examples include Postman, Insomnia, Hoppscotch, Bruno, HTTP Toolkit, and Thunder Client (the category leaders). Tools listed here emphasize ease of use, collaboration, automation, and support for REST, GraphQL, WebSocket, and gRPC.

Open-source emphasis: This section is heavily expanded with every major active project for self-hosting, local-first usage, full customization, and privacy-focused API testing — ideal for developers and teams avoiding vendor lock-in.

Contributions welcome! Open a PR to add/update entries. Keep descriptions factual and link to official sites.

Table of Contents

• SaaS Products
• Open-Source GitHub Projects
• How to Contribute
• Disclaimer

SaaS Products

Core Platforms (API Testing Tools)

• Postman
  The most widely used API platform with powerful collections, environments, mock servers, monitoring, and team collaboration features.

• Insomnia
  Clean, developer-friendly API client (now part of Kong) with strong support for GraphQL, gRPC, and environment management.

• Hoppscotch
  Lightweight, beautiful, and fast API request builder with real-time collaboration.

• Telerik Fiddler
  Popular HTTP debugging proxy for deep traffic inspection, breakpoints, and mocking.

• Requestly
  Modern API testing and modification tool with powerful redirect, modify, and mock rules.

Advanced & Specialized Platforms

• HTTP Toolkit
  Beautiful HTTP debugging toolkit with interception for mobile, browsers, and backend services.
• ModHeader
  Lightweight Chrome extension for modifying request headers during testing.

Other notable mentions: Thunder Client, Bruno (open-core), Redirector, and Resource Override.

Open-Source GitHub Projects

Dedicated API Testing & Debugging Tools

• Bruno
  Fast, open-source, Git-friendly Postman alternative. Stores collections in plain folders/files (no cloud lock-in) with excellent performance.

• Hoppscotch
  Fully open-source, lightweight API development suite with support for REST, GraphQL, WebSocket, and realtime collaboration.

• HTTP Toolkit
  Powerful open-source HTTP debugging proxy. Intercepts traffic from browsers, terminals, mobile devices, and Docker with ease.

• HTTPie
  Modern, user-friendly command-line HTTP client. Excellent for scripting and quick API testing.

• Thunder Client
  Lightweight, open-source Postman alternative built as a VS Code extension.

• VS Code REST Client
  Popular VS Code extension for sending HTTP requests directly from code files.

• Insomnia (Core)
  Open-source core of Insomnia with powerful plugin ecosystem.

• Newman
  Open-source command-line collection runner for Postman (great for CI/CD pipelines).

• Restish
  Modern CLI for interacting with REST services with automatic schema discovery.

Additional Strong Open-Source Options

• Karate DSL — Powerful API testing framework with BDD style.
• RestAssured — Java DSL for testing REST services.
• WireMock — Flexible API mocking and stubbing tool.
• Mockoon — Easy-to-use desktop API mocking tool.
• Parlel — 250+ service emulators (Stripe, Postgres, Slack, S3, Kafka and more) on local Docker, speaking real wire protocols so unmodified client libraries connect to localhost.
• Postwoman / Hoppscotch forks — Community maintained versions.
• curl + modern wrappers like httpie and xh.
• Paw alternatives and cross-platform tools.
• Testfully and other open-source API monitoring tools.

Frameworks for building custom tools: Combine Bruno or Hoppscotch with Newman, HTTP Toolkit, and CI tools (GitHub Actions) for complete open-source API testing workflows.

How to Contribute

1. Fork the repo.
2. Add/edit entries in README.md (follow existing format).
3. Include: name, link, 1–2 sentence description, and whether it's SaaS or open-source.
4. Submit PR with a short explanation.

Star the repo if you find it useful!

Disclaimer

• This is a community-curated list — not exhaustive and not an endorsement.
• Some tools have both open-source and paid cloud versions. Always check licensing for commercial use.
• When testing APIs, ensure you have proper authorization and respect rate limits and terms of service.

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