Google has introduced offline video playback for YouTube mobile users and it’s only available on Android devices in India, Indonesia or the Philippines at this point.
This feature lets you take videos offline to watch later during short periods of low or no internet connectivity. For videos where this feature is available, you can choose to add the video for offline viewing by tapping on the offline icon. Once taken offline, videos can be played back without an Internet connection for up to 48 hours.
Google hopes that making YouTube videos available for offline playback will help people move past the challenges of data connection and speed.
Source: Google Asia Pasific Blog