My testing by network sniffing confirms that no more HTML is returned from the Facebook servers but JSON, the preferred format when using REST technology. JSON just gives you the data, formatting needs to be done by the code inside of the app. Most iOS apps that retrieve server data use JSON technology, so that was a no-brainer. According to their development blog post, many more different optimisations were implemented, including offloading actions to background threads (iOS 101), caching of computations how long text should be displayed, caching of heights of rows in the UITableView. Most of the app is native now. Still some lesser used parts are leveraging HTML technology, to allow for flexibility.