How to remove it
Open the form's Connect → Deploy.
Click the trash icon button next to the domain name.
The domain is removed immediately. A toast confirms: '{domain} successfully removed.'
Connect → Deploy reverts to showing the Add Custom Domain input.
What happens after removal
The custom URL stops serving your form straight away. Any visitor who hits the old domain will see an error until you update or remove the A record at your registrar. The form's default URL (/f/your-slug) continues to work unaffected — the form is still live at that address.
Re-adding a domain
You can re-add the same domain to the same form — or a different form — at any time. The DNS records at your registrar do not need to change as long as they still point to 216.150.1.1.