The Login Button is a simple way to trigger the Facebook Login process on your website or web app.
If someone hasn't logged into your app yet, they'll see this button, and clicking it will popup a Login dialog, starting the login flow. People who have already logged in won't see any button, or you can also choose to show a logout button to them.
In addition to the settings above, you can also change the following:
If enabled, the button will change to a logout button when the user is logged in.
The maximum number of rows of profile photos in the Facepile when
The list of permissions to request during login.
Picks one of the size options for the button.
Determines whether a Facepile of logged-in friends is shown below the button. When this is enabled, a logged-in user will only see the Facepile, and no login or logout button.
Determines what audience will be selected by default, when requesting write permissions.
How do I use this to log users in?
There is no extra set up required here, however you can use the
Can I use the Login Button with server-side registration code?
authResponse object using
FB.getLoginStatus(). You can use this function to pass the response object to your server-side code to complete any registration that exists there.
Can I use the Login Button to re-request a permission that a person has declined?
The Login Button doesn't support re-requests because asking for declined permissions doesn't fit the verb on the button. If you need to re-request a permission, set up a custom button and use
FB.login() as described in the Facebook Login for the Web documentation.