Single Sign On is an improvement to the way you currently log into your mobile applications on Facebook. By providing your Facebook username and password information just once, you will now have one-click login access to all participating Platform applications on your mobile phone. You will no longer be required to input your login information separately for every single application, which can be a very time-consuming task on the phone.
This feature is currently available on all versions of Android and iOS devices running iOS4 or greater.
Prior to this feature, you had to provide your username and password information for every mobile application you used. With Single Sign On, you can dive right into your applications, making it easier to interact with people you know, see what your friends are up to, and share photos, news, and more.
Single Sign On is currently available on mobile applications from a select group of developers, including Groupon, Flixster, Zynga, and Yelp. The feature will expand to more applications in the future.
Using Single Sign On fin Facebook Mobile
When you open a participating application on Facebook mobile, you will see a “Login with Facebook” button. On your first time using the Single Sign On feature, you will be asked to allow the application to access your basic information. This is the public information that you share with everyone on Facebook, including your name, profile picture, gender, and friend list. Once you click “Allow,” you will be logged into the application.
Note: If you log out of the Facebook application, you will not be logged out of an application you’ve already logged into using this feature. Similarly, if you log out of an application you’ve logged into using Single Sign On, you will not be logged out of the Facebook application.
You will always be in control of whether or not to use the Single Sign On feature with a given mobile application. You must give your explicit permission for this login feature to work. To grant permission, select “Allow” in the permission request dialog when you first try to use this feature on an application. If you do not want to use Single Sign On with an application, simply click “Don’t Allow” in this dialog.
The Single Sign On feature is a feature that developers can choose to add to their application. We also encourage developers who build applications that contain sensitive, private, or financial information to apply appropriate safeguards to ensure this type of information is protected. [source]