API Tester

Test HTTP APIs with any method, headers, and body. A lightweight Postman alternative.

  • 100% free
  • Private in browser
  • No signup
  • No watermarks
One per line: Key: Value

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About API Tester

API Tester on TheToolss is a lightweight HTTP client that lets you test any REST API endpoint. Send GET, POST, PUT, PATCH, DELETE requests with custom headers and body. View response status, headers, timing, and body — all in your browser.

How to use API Tester

  1. Select the HTTP method and enter the API URL.
  2. Add headers (optional) and request body for POST/PUT/PATCH.
  3. Click Send and view the response details.

Key features

  • Supports GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS
  • Custom headers with easy key-value input
  • Request body support with auto JSON Content-Type detection
  • Response status, headers, body, timing, and size
  • Auto-formats JSON response bodies

Frequently asked questions

Does this replace Postman?
For quick API testing in the browser, yes! For complex workflows, collections, and environment variables, Postman is still recommended.
Can I send cookies or auth tokens?
Yes — add them in the Headers section. For example: Authorization: Bearer your-token-here