CORS Debugger
Paste request and response headers or a HAR file and see why the browser blocks a cross-origin request.
About this tool
Paste the request headers with Origin and the response headers, plus the preflight if there was one, or open a HAR file. The tool shows what the browser did and which Access-Control header does not match, with a fix for each.
Nothing is sent to the server you are debugging. Cookie, Authorization and Set-Cookie values are never shown, even when they are in the pasted headers or HAR. At most 5 MB of HAR is read.