Note: This only applies to forms using the legacy email-based URLs. If you registered and created your form online at Formspree.io, or with our CLI, you will not need to activate or confirm your form. For more information see phasing out legacy forms (email URLs).
When dealing with legacy forms we treat each combination of URL and email address as a different form. Each different form must be activated individually. So if you have your form appearing on https://your-site.com/contact and https://your-site.com/about, these are different forms and must be activated separately. The same if you have https://www.your-site.com/contact (note the extra `www` - that's a different URL so it looks like a separate form to us).
For non-legacy forms, when you create a form in the dashboard it's given a unique ID. The form's endpoint includes the ID instead of your email. When we receive a submission to that endpoint with its unique ID, we can look up the form directly, rather than checking the referring URL. That means we can treat it as the same form regardless of what page it's on.