Squarespace does not allow direct control of the built-in form action, so the most reliable integration is to use a Code Block with your own HTML form.
This gives you full control over field names and submission behavior.
Create a Formbase endpoint
Create a new form in the Formbase dashboard and copy the endpoint URL.
Add a Code Block
In Squarespace, add a Code Block to your page and paste an HTML form.
Set the action URL
<form action="https://formbase.dev/s/YOUR_FORM_ID" method="POST">
<input name="name" placeholder="Name" required />
<input name="email" type="email" placeholder="Email" required />
<button type="submit">Send</button>
</form>
Publish the page and submit a test entry.
If you need a custom success experience, handle submission with JavaScript and redirect manually.