Basics
Special fields
Reserved field names that change how FormBackend handles a submission
Most fields are stored as normal submission values. A few reserved names change routing, email behavior, or redirects. These apply to HTML forms posted to your FormBackend endpoint.
Special fields are not stored as regular submission values unless noted.
| Input name | email, e-mail, or email_address |
| Description | Address used when you enable submitter auto-responses. Without one of these fields, FormBackend cannot email the person who submitted the form. See Sending emails. |
<input type="email" name="email" required>
Redirect after submit
| Input name | _redirect or _redirect_to |
| Description | On paid plans that include custom redirects, send the submitter to this URL after a successful HTML submission. Overrides the form’s redirect URL setting. Also see Redirect after submission. |
<input type="hidden" name="_redirect" value="https://example.com/thanks">
You can interpolate submitted values into the redirect query string with {field_name} placeholders in the URL.
Reply-To for owner notifications
| Input name | _reply_to |
| Description | Sets the Reply-To address on the owner notification email when it differs from the submitter email field. Defaults to no-reply@formbackend.com when omitted. |
<input type="hidden" name="_reply_to" value="inbox@example.com">
Owner notification recipient
| Input name | _owner_to |
| Description | Overrides which address receives the owner notification for that submission. Useful when routing alerts from the form itself. Prefer conditional emails or form rules for durable routing. |
<input type="hidden" name="_owner_to" value="billing@example.com">
Owner notification subject
| Input name | _subject |
| Description | Overrides the subject line on the owner notification for that submission. |
<input type="hidden" name="_subject" value="Priority support request">
Honeypot and CAPTCHA fields
These are recognized by spam filtering and are stripped from stored values:
| Input name | Purpose |
|---|---|
formbackend_nono (or your custom honeypot name) |
Honeypot — leave empty; any value marks the submission as spam |
g-recaptcha-response |
Google reCAPTCHA token |
h-captcha-response |
hCaptcha token |
cf-turnstile-response |
Cloudflare Turnstile token |
See Spam filtering and the CAPTCHA guides under Spam for setup details.