Download videos and audio from YouTube in Chrome Browser on MAC and Windows computers
Add the Script Runner PRO extension from Google Chrome Web Store
Click this Install YouTube Downloader JS and after "Confirm Installation"
Youtube Downloader is Ready. Visit the video page on youtube.com and download the video
Select the audio and video quality of the video you want to download and click on the blue "Download Icon"
You can use LetVid's YouTube Downloader APK for your Android devices in addition to Chrome Extension, which downloads videos and audio from YouTube.