Google has announced a new feature for Google+ – third-party websites and applications can now offer sign ins through Google+.
The new Google+ Sign-Ins are essentially Facebook Connect for Google+, allowing you to not only sign-in to sites that support it, but also bring your Google+ profile data with you around the web.
The new Google+ Sign-In service will make it easier to share content from third-party sites (and within mobile apps). Exactly who will see the items you share on Google+ depends on the level of access you grant to an app, but in general you can share data with specific people on Google+, certain circles, or no one.
Here's Google's description of the actual sign-in process:
Google+ Sign-Ins aren't just for web apps either – Google is pushing them for mobile apps as well. Starting today, when you sign in to a website with Google, you can install its mobile app on your Android device with a single click.
Google is also claiming that, because you can choose who to share things with, that it will mean less "social spam." The Google+ Developer Blog even calls out Facebook's "frictionless" sharing by name, saying "Google+ doesn't let apps spray 'frictionless' updates all over the stream, so app activity will only appear when it's relevant." Of course one person's "relevant" content is another's spam, so take that claim with a bucket or two of salt.
Items you share from sites and apps using Google+ Sign-In show up as a slightly different "interactive" post in your friends' Google+ stream. Clicking on these items will lead them to the app where they can listen to or buy or review the item you shared.
If you want to add Google+ Sign-In to your site or app, head on over to the new developer site and read through the documentation.
