This extension adds a few quality of life features to the Web Dev Simplified course website.
The main thing saved is your video settings between videos and site visits so you don't need to manually set them each time. Below is a list of all the settings that are saved:
Playback Speed
Volume
Subtitles
The next big thing is the ability to autoplay videos. If you click on the extension in your toolbar you can enable the autoplay feature. This will automatically play the next video in the course when the current video ends. You can also change the delay between the current video ending and the next video starting to any value between 0 and 10 seconds.
