Signed-in devices and sessions

Your User Settings page has two tools for managing where you're logged in.

Remembered devices

When you choose to stay signed in, that device is remembered so you don't have to log in every visit. Remembered Devices lists them, and you can revoke any of them but the one you're currently using - useful if you signed in on a shared or public computer, or lost a device. To forget the device you're on right now, log out instead.

Sessions

The Sessions section has a single button that signs you out everywhere at once, ending every active session and remembered device. Reach for it if you think someone else may have access to your account - then follow up by changing your password.