Forms

A contact form on a static site, with no backend and no script: the form posts to Sitebin, and Sitebin emails each submission to one recipient, who agreed to receive them.

Add a form

On the site's edit page, open Forms and give the form a name and a recipient. The name is what the recipient sees as the sender of every message. The recipient gets one email to confirm; until they click it, the form refuses submissions. That confirmation is what keeps a form from ever mailing someone who did not ask for it.

Then copy the form's snippet into any page of the site:

<form action="/_sitebin/forms/k7f3m2q9xaw4npd6" method="post">
  <label>Name <input name="name" required></label>
  <label>Email <input name="email" type="email" required></label>
  <label>Message <textarea name="message" required></textarea></label>
  <input name="_gotcha" tabindex="-1" autocomplete="off" aria-hidden="true" style="position:absolute;left:-9999px">
  <button type="submit">Send</button>
</form>

The form posts to its own site — the site's address or your custom domain — so there is nothing to allow and nothing to load. Style it and add fields as you like: every field is forwarded, in the order the form has them.

Fields with a meaning

Captcha

Switch on Captcha and the snippet gains two lines: an ALTCHA widget and its script. The visitor's browser solves a small proof-of-work puzzle — no images, no tracking, no third party: the challenge and the script come from Sitebin itself. A solution is valid for five minutes, for this form only, once.

<altcha-widget challenge="/_sitebin/forms/k7f3m2q9xaw4npd6/challenge"></altcha-widget>
<script type="module" src="/_sitebin/altcha.js"></script>

If your page sets its own Content-Security-Policy, allow worker-src blob:: the widget solves in web workers.

Attachments

Switch on Attachments and the form posts multipart/form-data with a file field. Up to 5 files of 2 MB each travel with the mail. Executable files (.exe, .js, .bat, .msi and the like) are refused: mail providers reject whole messages over them.

What arrives

One email per submission, from the form's name, with an HTML and a plain-text part that lay out the fields in order, the attachments, and a stop link. Every mail also carries submission.json, for anything that reads mail by machine:

{
  "version": 1,
  "form": { "key": "k7f3m2q9xaw4npd6", "name": "Contact" },
  "site": { "id": "…", "host": "www.example.com" },
  "submitted_at": "2026-09-24T10:15:00Z",
  "fields": [
    { "name": "name", "value": "Anna Muster" },
    { "name": "email", "value": "anna@example.com" },
    { "name": "message", "value": "Hello!" }
  ],
  "files": [
    { "field": "cv", "filename": "cv.pdf", "content_type": "application/pdf",
      "size": 183244, "sha256": "…" }
  ]
}

fields is a list, so repeated names (a group of checkboxes) and the order survive. The visitor's IP address is not included. Sitebin keeps no copy: a submission is mailed and gone.

After sending

Without JavaScript the browser lands on the form's thank-you page — a path on the same site you set, such as /thanks.html — or a plain default page. If something is wrong (the form is not confirmed yet, a file is too large, too many messages in a short time), the visitor sees why, with a way back.

Submitting with your own fetch? Send Accept: application/json and get {"ok":true}, or {"error":"…"} with the status: 403 for a form that is not active or a failed captcha, 413 for too large, 429 for too many, 502 when the mail could not be sent — try again.

The recipient decides

Every mail has a Stop emails from this form link, and mail clients show their own unsubscribe button for it. A stopped form refuses submissions until the site's owner resends the confirmation and the recipient accepts again. Changing the recipient asks the new address first.

Limits

• Forms per site: Pro 1, Studio 10. When a plan shrinks, the newest forms pause — nothing is deleted — and resume when the plan allows again.
• 10 submissions per visitor per hour across all forms, and 60 per form per hour.
• 50 fields of up to 10,000 characters; 5 files of 2 MB.

API and agents

Forms are managed with the site's edit password or an account token: GET/POST /api/sites/{edit_id}/forms, PUT/DELETE …/forms/{key}, and POST …/forms/{key}/confirmation to resend — see the API. Agents have the same through MCP: list_forms, add_form, update_form, remove_form and resend_form_confirmation.

Self-hosting

Forms are open source, in every edition. Point SITEBIN_FORMS_SMTP_HOST at an SMTP server and set SITEBIN_FORMS_SMTP_FROM to the address mail leaves from; each form supplies the display name. This mailer is separate from the one that sends account mail. All variables are on the configuration page.

With accounts enabled, a tier also needs "trusted": true to get forms at all: an untrusted site is served with form-action 'none', which leaves a plain form nothing to post to. See Enterprise setup for the tier fields.