How to Track Scroll Depth on Your Website
For some businesses tracking the users, specific scroll depth can be very insightful. For example, I encourage all media publishers to enable some form of scroll depth on their website. It is one part of the equation for tracking if a user has read or seen your entire piece of content or article.
The table below is a good framework if you are going the custom implementation route. This would be a few events around scroll depth. The "Object Action" would be the event and "Properties" is the value associated with the event.
If you use Google Analytics as your primary analytics tool then I'd recommend using a third-party plugin that is documented really well here. I've used this before and had good results.