Google finally launched the Nexus 5 handset pre-installed with Android 4.4 Kitkat operating system last week.

Google has announced that the Android 4.4 update will be available for existing Nexus 4, Nexus 7 and Nexus 10 users. The update, however, will not be available for the Galaxy Nexus.

The official update, which will be available Over-the-Air, will be available soon, but the exact release schedule for the devices have not been revealed as of yet.

ROM developers have created unofficial upgrades for the Nexus 4 and Nexus 7 for those who want the new software now and cannot wait for the OTA update. The ROM updates are available for those who have experience installing ROMs.

Nexus 7 2 users can download the ROM from Rootzwiki while original Nexus 7 2 user can download it through Pananoid Android.

Android Authority has also provided details on how to access the ROM for Nexus 4 users.

The Android 4.4 KitKat update will also be available for the Galaxy S4 and HTC One in the coming weeks.

Google has launched the Android Quick Start Guide for Android 4.4 KitKat on its Google Play store.

The 53-page guide details information on the new features of Android 4.4 such as Google Now and Tap & Pay features.

The new Android 4.4 KitKat features are as follows:

• Refreshed interface with translucent status and navigation bars on home screen and white status bar icons/text, ability for apps to trigger the translucent appearance.
• Optimizations for performance on devices with lower specifications, Low RAM device API
• Printing framework
• NFC Host Card Emulation for emulating smart cards
• WebViews based off Chromium (feature parity with Chrome 30)
• Expanded functionality for Notification listener services
• Public API for developing and managing text messaging clients, ability to specify a default SMS app.
• New framework for UI transitions
• Storage access framework for retrieving content and documents from other sources
• Sensor batching, Step Detector and Counter APIs
• "Immersive" full screen mode, software buttons and status bar accessed with an edge swipe gesture
• Audio tunneling, audio monitoring, loudness enhancer
• Built-in screen recording
• Native infrared blaster API
• Expanded accessibility APIs, system-level closed captioning settings
• New experimental runtime virtual machine, ART