HTML Form Action — What It Does and How to Use It

<!-- Basic absolute URL action (recommended for forms POSTing to a backend service) -->
<form action="https://splitforms.com/api/submit" method="POST">
  <input type="hidden" name="access_key" value="YOUR_ACCESS_KEY" />
  <input name="email" type="email" required />
  <button type="submit">Send</button>
</form>

<!-- Relative URL action (same-origin POST to an internal endpoint) -->
<form action="/api/contact" method="POST">
  <input name="email" type="email" required />
  <button type="submit">Send</button>
</form>

<!-- formaction override on a per-button basis -->
<form action="/api/save-draft" method="POST">
  <input name="content" />
  <button type="submit">Save draft</button>
  <button type="submit" formaction="/api/publish">Publish</button>
</form>

The `action` attribute on a `<form>` element is the URL the browser POSTs to when the form is submitted. It can be an absolute URL (`https://splitforms.com/api/submit`), a relative URL (`/api/contact`), or — historically — a `mailto:` URL. If `action` is omitted, the form posts to the current page URL.

Per the HTML specification (WHATWG §4.10.21.1), the `action` attribute determines the 'form submission URL' for the form. The browser appends form fields to that URL (as query string for GET, as request body for POST) and navigates to it. The user-facing behavior is the standard form-submit page transition: the new URL loads, often with the server returning a redirect to a thank-you page.

The `formaction` attribute (HTML5) lets individual submit buttons override the form's action. Useful for forms with multiple actions — Save Draft vs Publish, for example, can POST to different endpoints from the same form HTML. The button's `formaction` wins over the form's `action` when that specific button is the one that triggered submission.

Common gotchas: (1) `mailto:` actions are broken on most modern devices — the visitor needs a configured email client, which most don't have. Use a form-backend service instead. (2) Cross-origin POSTs require the destination to send permissive CORS headers; splitforms's endpoint does. (3) If you set the action to a 404 URL, the browser still POSTs and shows the 404 page — debug by testing with `curl -X POST` first.

Action URL, method POST, splitforms backend — three attributes, working form.