What type of opt-in permission is granted when a user submits their email through a form on a website?

When a user submits their email through a form on a website, they are typically granting single opt-in permission. This means that their action of entering their email address is sufficient for them to be added to the mailing list. The user does not need to take any further action to confirm their subscription, such as clicking a confirmation link sent to their email. This method is straightforward and allows for immediate inclusion in email communications, making it a common practice for many online services.

In contrast, double opt-in would require the user to confirm their subscription via an email link, adding an extra layer of verification which can lead to a more engaged subscriber list but may reduce the immediate number of subscribers. Verified opt-in is similar to double opt-in and focuses on ensuring that the subscriber is indeed the owner of the email address, which again involves an additional step. Implicit opt-in generally involves situations where consent is assumed through user behavior rather than explicitly provided through a form, which differs from the clear action of submitting an email through a form.

Thus, the act of simply submitting an email through a form directly supports the definition of single opt-in.