Two-factor sign-in

Turning it on

1. Open Your profile from the account menu at the foot of the sidebar.
2. Under two-factor authentication, turn it on.
3. Scan the QR code with an authenticator app on your phone, or type the setup key into it.
4. Name the authenticator, for example after the phone it is on.
5. Enter the six-digit code the app now shows.

What changes

Turning it on signs you out on every other browser and device. You stay signed in where you are, and from then on signing in asks for a code as well as your password, so a stolen password alone does not open your account.

You can add more than one authenticator, and any of them can give the code.