HTTP
CORS Checker
Check Access-Control-* headers. Verify Allow-Origin, credentials, methods, headers.
Fetches headers from our server — checks CORS configuration.
How to use
- Enter a domain, URL, or value relevant to CORS Checker.
- Run the check and review the output carefully.
- Apply recommended fixes, then run the check again to verify.
Common use cases
- Pre-deployment validation for CORS Checker.
- Incident triage when security checks fail in production.
- Periodic security review as part of technical SEO and hardening.
Example inputs
https://api.example.comCommon issues and fixes
Access-Control-Allow-Origin: * with credentials
Browsers reject wildcard with credentials. Specify exact origins instead of *.
Missing Access-Control-Allow-Methods
Preflight fails if methods are not listed. Add GET, POST, etc. as needed.
CORS blocking API calls
Backend must send Access-Control-Allow-Origin. Configure your server or proxy.
Recommended remediation
Add CORS headers on the server. For credentials use specific origins, not *. Use Vary: Origin. Test preflight with OPTIONS.
FAQ
Is CORS Checker free to use?
Yes. This tool is free and can be used without account registration.
Do you store submitted values?
Only the minimum processing needed for the check. For client-side tools, data stays in your browser.
How should I use these results?
Use the output as a diagnostic baseline, apply fixes in your stack, then re-run the check to confirm remediation.