CORS Tester | Test Cross-Origin Requests From Your Browser

CORS tester checks whether a URL allows cross-origin requests from your browser, and explains exactly why a request was blocked when it fails. Free, no signup.

Also known as: cors tester · test cors online free · check cors headers online · cross origin request tester · cors policy checker · access control allow origin checker · test cross origin fetch

ssl and security tools

api and http tools

url and link tools

networking

Request

Target URL

Method

Send credentials (cookies)

Testing from origin .... The request runs as a real fetch from this page, so the result reflects exactly what your own site would see calling this URL.

POST, PUT, and DELETE, or a credentialed request, may trigger a preflight OPTIONS request that the browser sends automatically before this one.

Result

Enter a URL and press Test CORS to see whether this origin can read its response

About CORS Tester

Test whether a URL allows cross-origin requests from your browser, see whatever Access-Control response headers the server exposes, and find out why a request was blocked. The test runs as a real fetch from this page, so it reflects what your own frontend would actually experience.

Key Features

Sends a real cross-origin fetch and reports whether the browser let the response through, since that success is itself proof the CORS check passed
Reads back any Access-Control-* headers the server chose to expose via Access-Control-Expose-Headers, and explains why they are usually invisible to JavaScript even on an allowed request
Distinguishes a CORS policy rejection from an unreachable server or network error by re-probing the same URL in no-cors mode
Choose GET, POST, PUT, DELETE, or HEAD, and optionally include credentials to test an authenticated cross-origin call

Use Cases

Debug a fetch() call that fails silently in the browser console with no useful error message
Verify a new Access-Control-Allow-Origin configuration actually permits your frontend's real origin before deploying
Check whether a third-party API can be called directly from client-side JavaScript or needs a server-side proxy

Related Keywords

cors tester

test cors online

check cors headers

cross origin request tester

cors policy checker

access control allow origin checker

test cross origin fetch

cors error debugger

Runs from your browser

The request is a normal fetch() sent directly from this page to the URL you enter. DevToolLab's servers are never involved and never see the target URL or the response.

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Frequently asked questions

What is CORS Tester used for?

CORS tester checks whether a URL allows cross-origin requests from your browser, and explains exactly why a request was blocked when it fails. Free, no signup.

Is CORS Tester free to use?

Yes. CORS Tester is completely free with no usage limits, and there is no paid tier required to use it.

Do I need an account to use CORS Tester?

No. CORS Tester works immediately in your browser with no signup, login, or email address required.

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