You can easily display the FB login button on an app or website in order to allow users and visitors to log in, and also show their profile pictures and pictures of friends who have already logged in for the app or website.

The Facebook login button allows customization to a certain degree, for example, you can specify the maximum number of rows of faces the button displays, so after specifying the number of rows of faces you want to show the plugin will automatically and dynamically size its height.

If you’re using the new JavaScript SDK, the plugin is available via the XFBML tag or the HTML tag.

“If show-faces=true and people viewing your app or site are already logged in, they won’t be shown a login button.”

FB Login Button Attributes:

- show-faces – specifies whether to show faces underneath the Login button.
- width – the width of the plugin in pixels. Default width: 200px.
- max-rows – the maximum number of rows of profile pictures to display. Default value: 1.
- scope – a comma separated list of extended permissions.
- registration-url – registration page url.
- size – Different sized buttons: small, medium, large, xlarge (default: medium).

If you want to add the Facebook Login button to your app or website visit this page to get the code.