Why use CORS Checker?
Cross-origin failures are frustrating because the browser hides details. This checker performs a preflight-aware request, surfaces Access-Control-* headers, and explains common misconfigurations such as missing methods, wildcard credentials, or mismatched origins.
Practical tips
- Test with and without cookies if your API uses credentials: include.
- Verify both OPTIONS and actual methods; some gateways only configure one.
- When providers block browser probes, enable the CORS proxy and compare behavior.
Common questions
- Does a successful check mean every client works?
- It validates the response you see from this environment. Mobile WebViews and extensions can still differ.
- Why does curl succeed but the browser fail?
- curl is not subject to CORS. Browsers enforce extra rules to protect user data on other sites.