If you are using Android. You can try Tube Plus.
Tube Plus is an app that helps you download YouTube videos in a really fast and comfortable way. You can save any file in your local storage or SD Card in a matter of seconds. Stop worrying about wasting your mobile data when you’re not in a WiFi zone!
Using Tube Plus is simple and its interface has been specially designed so you can browse through the platform with total ease. On the left side of the screen you’ll find a drop down menu where you can choose the topic that you’d like to browse, from vehicles to travel and music, education, comedy, animals or science and many others. The app also includes a search bar that helps you narrow down your search or the topic you’re interested in and a ‘trending’ system where you can take a look at the most popular videos within the last couple of hours.
Once you’ve located the element that you want to download, you just need to click on the arrow that’s at the bottom of the video and pick the quality you’d like. You can choose exactly how you want to watch your video, but do keep in mind that the higher the quality is, the more space it’ll take up in your smartphone’s memory. In a matter of seconds you’ll have a video that’s ready to be played at any moment and without needing an internet connection.
The best thing about Tube Plus is that you'll always have the highest quality available so you can enjoy your favorite shows or youtubers in amazing resolution. Also, you can use the video share and like system as well as browsing the rest of the options available in this great video platform. Basically, think of Tube Plus as a YouTube channel but with the added bonus of being able to download elements with it.