Test REST APIs online — like Postman in your browser. GET, POST, headers, auth, response viewer and code snippets
Built & maintained by Pappu Venkata Subbi Reddy, founder of Clacify · Updated July 2026
API Tester lets you test REST APIs directly in your browser — like a lightweight Postman with nothing to install. Enter a URL, choose the method (GET, POST, PUT, PATCH, DELETE), add custom headers and a request body, and send the request to see the response status, headers, timing, and formatted JSON body. It's ideal for developers debugging endpoints, checking integrations, or exploring a public API quickly. Requests go directly from your browser to the API; nothing is routed through or stored on our servers.
The tool uses the browser's native Fetch API to send your request with the chosen method, headers, and body, then displays the response status, headers, round-trip time, and body (auto-formatting JSON). Because it runs in the browser, cross-origin (CORS) policies set by the target API apply, just as they would for any web client. No request or response data is logged or proxied through our servers — it's a direct browser-to-endpoint call.
| Code | Meaning | What it usually tells you |
|---|---|---|
| 200 OK | Success | The request worked; response body has your data |
| 201 Created | Success | Your POST created a new resource |
| 204 No Content | Success | Worked, but there's nothing to return |
| 400 Bad Request | Client error | Malformed request — check your body/params |
| 401 Unauthorized | Client error | Missing or invalid auth token |
| 403 Forbidden | Client error | Authenticated, but not allowed |
| 404 Not Found | Client error | Wrong URL or the resource doesn't exist |
| 429 Too Many Requests | Client error | Rate limited — slow down |
| 500 Internal Server Error | Server error | The API crashed — not your fault |
Rule of thumb: 2xx = success, 3xx = redirect, 4xx = you sent something wrong, 5xx = the server broke.
GET reads data and should never change anything. POST creates a new resource (submitting a form, adding a record). PUT replaces an existing resource wholesale, while PATCH updates just the fields you send. DELETE removes a resource. Pick the method that matches your intent — many APIs reject a GET where they expect a POST, and using the right verb is half of designing a clean REST API.
If a request works in Postman but fails here with a CORS error, that's expected — and it's not a bug in the tool. Browsers enforce Cross-Origin Resource Sharing: an API must explicitly send an "Access-Control-Allow-Origin" header permitting other websites to call it. Desktop tools like Postman aren't browsers, so they skip that check. If you're testing your own API, add the right CORS headers; if it's a third-party API without them, you'll need a server-side call.
A useful test looks at three things: the status code (did it work?), the round-trip time (is it fast enough?), and the body (is the data shaped the way you expect?). This tester auto-formats JSON responses so nested data is readable at a glance, and shows the response headers — where you'll find rate-limit counters, content types, and auth challenges that explain a lot of "why isn't this working" moments.
Use Clacify's API Tester — enter the endpoint URL, select the HTTP method (GET, POST, etc.), add any headers (like 'Authorization: Bearer yourtoken' or 'Content-Type: application/json'), add a request body for POST/PUT, and click Send. The response appears with status code, response time, and formatted body.
GET: retrieves data from a server — parameters go in the URL. Should be idempotent (multiple identical requests have the same effect). POST: sends data to create/update a resource — data goes in the request body (JSON, form data). Not idempotent — sending the same POST twice typically creates two records. Use GET for reading; POST/PUT/PATCH for writing.