Sony has started to roll out the Android 4.4 KitKat update for its Xperia Z1 Ultra, Xperia Z1, and Xperia Z1 Compact handsets.

The company has also offered a complete changelog for the update, detailing the new features and functionality the new firmware build brings to the table.

Sony has revealed that it has already started to push out the Android 4.4 update for the Sony Xperia Z1, Z Ultra, and Z1 Compact and provided the full changelog for the update. There will be an improved performance and user interface, new and improved status bar, Quick settings, and much more.

"The next Sony software rollout for Xperia Z Ultra, Xperia Z1 and Xperia Z1 Compact starts right about now," the company announced on Wednesday, March 19. "We've been working to build new Sony experiences on Google's KitKat release to create some neat / sweet features (if we say so ourselves)."

The update will come with the usual performance tweaks, but also some new functionality aiming to improve the user experience. Here's the complete changelog, as Sony listed it:

• Android 4.4 KitKat, with the standard performance and user interface (UI) optimization;
• Sony's tweaked Status Bar and Quick Settings, which the company now touts as more intuitive and customizable. Sony claims that the new look is cleaner, ensuring that users only get the notifications they need, without any clutter;
• New UI similar to that of the Sony PlayStation 4, sporting the same sleek launch animation and live wallpaper across the home and lock screens;
• Updates in Sony's native app portfolio, with enhanced functionality for Messaging, MyXperia, Smart Connect, Small Apps, TrackID, TrackID TV, Sony Select, Smart Social Camera, and more;
• Enhanced Sony Media apps: WALKMAN, Album and movies, with Sony Entertainment Network cloud service integration. According to Sony, the latest update will bring a "more converged entertainment experience," complete with Sony Entertainment Network & PlayMemories integration that offers an improved UI, faster downloads, and more;
• Sony "Xperia Themes" bring downloadable UI packs from Sony Select for a unique custom interface experience;

The update package is currently rolling out to the Sony Xperia Z Ultra, Xperia Z1, and Xperia Z1 Compact in phases, which means that it may take a few days for the new firmware to reach all devices.

Sony will continue to roll out Android 4.4 KitKat to other handsets as well, with the Xperia Z, Xperia ZL, the Xperia Tablet Z, and Xperia ZR set to get a software bump from mid-second quarter.

Moreover, Android 4.4 KitKat will also hit the Sony Xperia T2 Ultra, Xperia E1, and Xperia M2 devices, with more details to follow at a later date. Keep in mind that the timing and availability of the update may vary by market and carrier.