The feature, which the online search engine started rolling out Tuesday, lets people change their personal settings, so they can access multiple Gmail, Calendar, Reader, Code or Sites accounts. The feature is unavailable to other Google accounts.
Before the change, people who had two Gmail accounts, for example, had to log out of one, in order to log in and access another. With the new feature, the email account a person is on is listed at the top of browser-based client. When a person clicks on the account, the other accounts can be accessed from a dropdown list.
There are some quirks with the new feature. For example, multiple sign-in is unavailable on mobile devices and offline Gmail and offline Calendar are disabled. Nevertheless, the feature could be a time saver for people with several accounts.
To turn-on the feature people must first go to Personal Settings in My Account, click on "Change" next to Multiple Sign-In and follow Google's instructions. The feature is turned off by default.
While the new capability is not technically single sign-on in that you can access all multiple Google accounts after signing in once, the feature marks a step in that direction. Google researchers recently proposed a system called PseudoID that uses blind cryptographic signatures to generate a pseudonym to log into multiple Web sites through a federated identity system without revealing the user's identity.
Google offered the proposal as a way to prevent online identity providers from amassing information about Internet users that could harm user privacy if exposed. The paper was presented at the 10th Privacy Enhancing Technologies Symposium in Berlin, Germany.