Go to your Google Account. On the left navigation panel, select Security . On the Your devices panel, select Manage all devices. You'll see devices where you're currently signed in to your Google Account or have been in the last few weeks.

But you might be wondering, “How many Gmail accounts can I have?” Using multiple Gmail accounts is an effective way to keep messages organized for different businesses and projects, but is there a limit? Luckily, there's no limit to the number of Gmail accounts you can have.

Go to http://accounts.google.com/signin/usernamerecovery and enter any email accounts or phone numbers that you've had for a while and which may have been used as recovery info. The “find your email” page can help you locate any forgotten Google accounts.