Facebook a new version of its login system for third-party apps that lets people log in anonymously so they can demo apps before they provide their personal data. The new login also gives you total granular control over what data types you give an app.
In addition, Facebook’s login service for mobile apps now offers users more fine-grained controls over what they share with an app. Users can’t just decide whether an app can publish to your news feed and what date it can read from it, but they will have very precise controls over what exactly gets shared.
Even with the anonymous identifier, your experience between apps can still be synced, but the app won’t get any personal information from you. This works because Facebook still uses a unique identifier for you every time you log in anonymously. That way, even if an app doesn’t know your name, it can save your content, high scores, or ther data and sync it across devices.
If you don’t use the anonymous login, the new permission dialog now allows you to go through your permissions line by line.