Frontend Masters JavaScript is an Android app that provides access to over 150 web development courses. The app is free and offers courses on the most important JavaScript and front-end development skills such as React, Node.js, Vue, Functional JavaScript, CSS Grid, Flexbox, and more. The courses are taught by experts in the field and are regularly updated with new content.

One of the best features of the app is the ability to save videos to your device and watch them on-the-go, on or offline. This is especially useful for those who want to learn while on a plane, train, or in areas with limited internet connectivity. The app also syncs your progress online and offline, so you never lose your place.

Overall, Frontend Masters JavaScript is a great app for those looking to improve their web development skills. With its comprehensive course catalog and convenient offline viewing options, it's a valuable resource for both beginners and experienced developers alike.