Time tools is the best tool that allows you to analyze YouTube videos and track the total time spent watching videos and time saved when using faster playback rates.

The app has 3 modes: normal mode, video speed, and pause/resume. You can use video speed or pause/resume to track watch time and time saved.

When you enable video speed you can watch a video at faster speeds, and the app will shift the current time marker for you.

Additionally, you can now watch a 30-minute video at 2x speed and the duration marker will scale to show a new duration of 15 minutes. This is a Google Chrome extension, you must be using Chrome as your browser.