Google+ has made three changes to its Sign-In service that should make it more appealing to developers. First, users no longer need to have a Google+ account in order to use Google+ Sign-In for other apps.
Second, the company says its new migration features and guides make it much easier to convert from OpenID v2 or OAuth 2.0 Login to Google+ Log-In.
And third, Google is adding an “incremental auth” feature. It allows developers to ask for some basic permissions up front when a user downloads an app and then to ask for additional permissions later if they are needed when users access certain app features.