While YouTube users in the United States, Canada and other parts of the world have to subscribe to YouTube Red to gain the ability to save videos offline, Google has been offering this functionality for free to YouTube users in India. 

This is because of the poor internet connectivity in the country. Now, the company is further improving this feature with the addition of Smart Offline. The feature takes advantage of the cheaper data rate that many mobile operators offer in India during night hours. So, Smart Offline makes sure that the video is downloaded overnight when data rates are lower. You get the option of saving videos overnight when you tap on the save offline button in the YouTube app.

For now, Google is rolling out this feature for all Airtel and Telenor (Uninor) subscribers in India, though Google plans on bringing it to all YouTube users in India eventually. The feature only works over mobile data, so you are not going to get the option of saving videos overnight when your device is connected to a Wi-Fi network.

Also, make sure to update the YouTube app to the latest version from the Google Play Store if you are not seeing the Smart Offline feature on your Android device.