I hit the device limit — how do I free a slot?

Press Deactivate on a device you no longer use. The slot frees immediately and the next sign-in takes it.

Last seen is the column to read. A device last seen two months ago is the one to free; one last seen this morning on a machine you still use is not.

The usual culprits are a machine you replaced, a browser whose data you cleared, a work computer, or a private window you signed in from once.

You can deactivate the device you are on, and doing so signs that browser out — which is occasionally what you want and usually not. The THIS DEVICE badge is there to stop you doing it by accident.