Web & Networking Tools
CORS Policy Tester / Explainer
Test CORS headers on any URL and get a plain-English explanation of the policy.
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What is CORS Tester?
CORS controls which origins can access a resource from a different origin. This tool makes a cross-origin request and reports the Access-Control-* headers.
How it works
We attempt a fetch with credentials and report the response headers, matching them against your origin to tell you whether the request would succeed from your current context.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.