Why Is Multiple Sign-in such a good idea?
Suppose you have two Gmail addresses that you use for different purposes. Traditionally, you can use only one at a time. For viewing another inbox, you have to sign out from one Google account and then sign in into another. With multiple sign-in feature, you can directly access the second Gmail inbox without signing out from the first one.
How to Sign in to Multiple Google Accounts?
To use separate Gmail/Google accounts in the same window, you will have to add an account on top of already logged in account. First, open any Google product (Google search, Gmail, Drive, Map) and click on your name or picture on the top right-hand side. Select Add Account from the drop-down.
Alternatively, you can go to https://accounts.google.com/AddSession and add/remove accounts. After enabling multiple sign-in (linking different Google accounts), you can see a drop-down along with your current Gmail id at the top-right corner of the browser, which will let you choose other Gmail without login-out from the first one. According to Google Support, Google uses cookies for the sign-in process. Based on the cookie value, you can use only one account at a time. However, Multiple Sign-in allows you to use more than one account at a time in the same browser. Please note that these simultaneous logins will not work on all Google services. The currently supported products are: Also, Multiple Sign-in is not available for offline Gmail and offline calendar. PS: It is better to check your current Gmail address before sending a mail. Current Gmail address is at the top-right corner in the browser or at the bottom in the mobile client. Via – Source 1, Source 2