Each of the following tags verify in some way the permissions for a user’s role on Facebook. These tags can be quite useful for virally promoting your app. For instance, if you want to encourage non-app users to install your app, use the <fb:visible-to-added-app-users/> tag in your application’s profile box to provide a message that encourages non-app users to add your application. Or, if you want to provide an admin interface that allows the owner of an app or the admin of a page to administer settings within your app, use the <fb:if-is-user/> tag with a uid of profileowner, and only the user who added your app will have access to those settings.

In this section, we will define the specifications of each authorization-related FBML tag on Facebook. The first half of the tags render only on a user’s canvas page or on a canvas page for a Facebook Page. The second half of the tags render only on a user’s profile or on a Facebook Page; they will not render on a canvas page. Each section in this chapter includes a brief description of the tag, followed by required and optional attributes that can be passed to the tags, as well as examples of how those tags can be used.