Features
Special fields
Field names that start with an underscore (_) are reserved control fields. They configure how the submission is delivered without showing up in your email body or dashboard.
| Field | Type | Description |
|---|---|---|
_subject | string (≤ 200 chars) | Override the email subject line for this submission. Defaults to “New submission: <form name>”. |
_replyto | email | Address used in the email's Reply-To header. If omitted, we auto-detect from a field called email, Email, e-mail, or from. |
_cc | email or comma-separated emails (max 5) | Add one or more CC recipients to this submission's email. Bounded to 5 to discourage abuse. |
_bcc | email or comma-separated emails (max 5) | Add BCC recipients. Same limits as _cc. |
_redirect | absolute URL | After a successful submission, redirect the browser here instead of showing our generic confirmation page. |
_next | absolute URL | Alias for _redirect. Useful for migrating from Formspree-style integrations without changing your HTML. |
_gotcha | string (must be empty) | Hidden honeypot field. If a bot fills it, the submission is silently discarded with a 200 OK. See Spam protection. |
_uploadIds | comma-separated upload IDs | Used by the direct-to-storage upload flow. See File uploads. |
Putting it together
html
<form action="https://formto.email/f/YOUR_FORM_ID" method="POST">
<input type="hidden" name="_subject" value="New homepage lead" />
<input type="hidden" name="_cc" value="sales@yourcompany.com" />
<input type="hidden" name="_redirect" value="https://yourcompany.com/thanks" />
<input name="name" required />
<input name="email" type="email" required />
<textarea name="message" required></textarea>
<!-- Honeypot for bots -->
<input type="text" name="_gotcha" style="display:none" tabindex="-1" autocomplete="off" />
<button type="submit">Send</button>
</form>Why underscores?
We reserve the underscore prefix so the values you control (like the Reply-To email or redirect URL) can never collide with your actual form fields. None of these underscored fields are stored on the submission or shown in the email body — they configure the email itself.