PrimeUtil

API Tester

A fully browser-based API testing tool. Choose any HTTP method (GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS), enter a URL, add query parameters, custom headers, a JSON or form body, and authentication (Bearer token, Basic auth, or API key). Hit Send and instantly see the status code, response time, response size, formatted body, and response headers. No backend, no signup — everything runs locally in your browser.

Query parameters — appended to the URL automatically. Supports {{variables}}.

Enable Use server proxy in Request settings to call APIs that block browser CORS. Private and localhost URLs are blocked on the proxy for security.

Features

  • All HTTP methods: GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS
  • Query params, custom headers, and auth helpers (Bearer, Basic, API Key)
  • JSON, form-data, x-www-form-urlencoded, and raw body types
  • Response status code with color coding, time, and size
  • Auto-formatted JSON response body with copy button
  • Response headers inspector
  • Runs entirely in the browser — no server, no signup

Frequently Asked Questions

Why am I getting a CORS error?
Browsers block requests to APIs that do not include CORS headers allowing your origin. This is a browser security restriction — not a tool limitation. To work around it, test APIs you own (and add CORS headers), use a CORS-enabled proxy, or install a browser extension that disables CORS for development.
Is my API key or token stored anywhere?
No. All data — including tokens, keys, and request bodies — stays entirely in your browser's memory and is never sent to PrimeUtil servers. Refreshing the page clears everything.
Can I send a POST request with a JSON body?
Yes. Select POST (or PUT/PATCH) as the method, open the Body tab, choose 'json', paste or type your JSON payload, then click Send. The Content-Type: application/json header is added automatically.
Does it support file uploads?
The form-data body type lets you send text fields as multipart form data. Binary file uploads are not yet supported in this tool.

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