I had to watch 19 hours of slow paced videos for a training on a new software product (at least new to me). I like fast paced trainings… enter a browser hack.
In Firefox, Navigate to Tools > Browser Tools > Web Developer Tools
Type the following snippet to find the first video on a page, and change the playback rate, and Click Enter.
document.getElementById(document.getElementsByTagName('video').item(0).id).playbackRate = 4.0
Note, 4.0 can be unintelligible, you’ll need to tweak the speed to match what you need. I found 2.5 to 3.0 to be very comfortable (you just can’t multitask).