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Start by submitting the smallest possible request, then add your fields and files back one at a time.
After it succeeds, open Submissions and confirm that the test response arrived.

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Missing or invalid Public Key

Copy the current Form endpoint URL from the Endpoint form’s General tab. The URL must end with that form’s Public Key; do not put the Public Key in the request body or an Authorization header.

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A 403 with domain_not_allowed

Domain restriction is on and the request’s Origin or Referer is not in the allowed list. Add the domain in the form’s Settings, or turn on Allow localhost if you are testing locally. Calls from a server or curl carry no Origin, so they fail while the restriction is on; turn it off for that form or send the request from an allowed site.

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The request succeeds but fields are missing

  • Give every HTML input, select, and textarea a name.
  • Make names unique unless you intentionally want several values under one label.
  • For JSON, send an object rather than an array or plain text.
  • Check that your JavaScript creates the payload after the latest values have been entered.

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The page leaves your website

A normal HTML post opens the default confirmation page. Add a hidden redirect field with a complete https:// URL, or submit with JavaScript and display your own success state.

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The browser shows an error page

If you submit with JavaScript, inspect the response status and message. Common causes include:
  • malformed JSON;
  • domain restriction rejecting the request’s origin;
  • a closed Endpoint form or scheduled close date;
  • an exhausted monthly response allowance;
  • an expired, missing, or rejected CAPTCHA token;
  • an unsupported, oversized, or over-limit file upload.

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A JavaScript form always looks successful

fetch() does not throw automatically for responses such as 400, 402, or 403. Check response.ok before showing a success message.

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The response arrived more than once

Disable the submit button while a request is in progress and restore it only after an error. A normal HTML submission uses a redirect-after-submit flow, so refreshing the confirmation page does not submit the form again. If the issue continues, contact support from your account. Include the form name, the approximate time of a test, the request content type, and the returned status and message. Do not send account passwords or CAPTCHA secrets.