How to track scroll depth with Google Tag Manager

There are lots of things you can do using Google Tag Manager. Check this blog on how to set up scroll tracking using Google Tag Manager. 

STEP 1: Enable Built-In Variables

Navigate to 'Variables' and click 'Configure' in 'Built-In Variables' section, Then 
go to 'Scrolling' Section tick/select ‘Scroll Depth Threshold’, ‘Scroll Depth Units’ and ‘Scroll Depth Direction’ variables.

STEP 2 - Create Scroll Depth Trigger

Create a new trigger for scroll depth, select Trigger Type 'Scroll Depth' and select vertical Scroll Depths. Add Percentage i.e. 10,25,50,75. Fire on all pages and save. 

STEP 3 - Create Tag to send scrolling events to Analytics

a) Add a new Universal Analytics event tag and select google analytics tag, select 'Event from Track Type drop down

b) Add appropriate values for category, action, and label. Add % in Action. 

c) If you do not want scroll events to impact your bounce rate at all, you should toggle the Non-Interaction Hit field to True.

d) Trigger this in all pages

Check this Video tutorial for more details