Even though Samsung released the latest Android version for the Galaxy Note 3 a few weeks ago, the roll out of the Samsung Galaxy S4 Android 4.4.2 update still hasn't begun. Fortunately, those of you who want to taste Android 4.4.2 on your Samsung Galaxy S4 terminals can install the I9505XXUFNAD test firmware that leaked courtesy of Sammobile.
Because most of the software features brought by Galaxy Note 3 were patched in the Android 4.3 Jelly Bean update for Samsung Galaxy S4, the new KitKat-based firmware only brings a couple of minor UI changes and the usual KitKat goodies. After you install Android 4.4.2 I9505XXUFNAD on your Samsung Galaxy S4 you will notice that the status bar has became transparent, that the status bar icons are now white, and that the album art is now displayed full-screen in the lockscreen. Among performance improvements and bug fixes, the new firmware also brings a quick-access camera button in the lockscreen, Printing option in Settings menu, emoji support, improved Samsung keyboard, and other such treats.
If you want to try the Android 4.4.2 I9505XXUFNAD test build on your Samsung Galaxy S4 you can download it from here and flash it on your device using Odin. Note that the leaked firmware is only compatible with the Snapdragon 600-powered Galaxy S4, codenamed I9505.
You should also know that this test firmware will wipe the data on your device, thus proceed on your own risk. If you previously flashed stock Android ROMs on your Galaxy S4 you probably know the drill: back-up your data, download the update file, extract it, restart your S4 in download mode, plug it in to your computer via USB, add the extracted files in Odin to AP, BL, CP, and CSC, respectively, make sure re-partition is not ticked, hit the start button, then wait a couple of minutes.
Anyway, if you have no idea what you're doing, it's recommended to wait until the official update is rolled out, then update your smartphone via Kies or OTA.