Form Endpoint CORS Tester: Diagnose CORS Errors
Test whether a form endpoint accepts cross-origin AJAX submissions from your site — diagnose CORS errors in seconds from your browser.
Form Endpoint CORS Tester: Diagnose CORS Errors
Enter your form endpoint URL and this tool performs a test POST from your browser. If the endpoint returns a CORS error, your backend’s allowed-origins list is missing your origin — add it (Form2Lead: the form’s Allowed Domains setting) and re-test.
What this test checks
- 1. The endpoint responds to a POST with an
Accept: application/jsonheader. - 2.The browser allows the response — if the backend's allowed-origins list omits your origin, you'll see a CORS error.
- 3. Add your site origin to Allowed Domains (Form2Lead) and re-run until green.
Tool FAQ
Is my form data sent when I test?
The test sends an empty payload with an Accept: application/json header to check the CORS handshake. Real submissions from your site will still work normally once the origin is allowed.
Why does my plain HTML form work but the tester shows a CORS error?
Plain HTML form POSTs are not subject to CORS — only fetch()/XHR requests are. The tester checks the AJAX path, which needs an Accept: application/json header and an allowed origin.