If you are not using suppression management with Unsubscribe Groups, it is the default functionality to unsubscribe a user at the global level when they click unsubscribe links.

When using Unsubscribe Groups, a recipient clicking an unsubscribe link can choose which groups to unsubscribe from, called a “group unsubscribe”, or may choose to opt out of all emails, called a “global unsubscribe”.

You can manage your global unsubscribes via Email Reports > Unsubscribes in the SendGrid UI.

Group Unsubscribes will trigger Event Webhook events.