How to track scroll depth in GA4 with GTM

GA4 gives you one scroll event out of the box, at 90% of the page. If you want to know how far people really get, 25, 50, 75, 100%, you set it up in Google Tag Manager with GTM's scroll trigger.

What GA4 does by default

Enhanced measurement fires a single scroll event when a visitor reaches 90% of the page depth. That is useful as a rough engagement signal but tells you nothing about the 10, 30 or 60% marks where people actually drop off.

Proper scroll tracking in GTM

1. In Google Tag Manager, enable the Scroll Depth trigger with vertical thresholds of 25, 50, 75, 100%.
2. Create a GA4 event tag, for example scroll_depth, that fires on that trigger and sends the percentage as a parameter.
3. Register the parameter as a custom dimension in GA4 so you can break reports down by depth.

Do not fool yourself with it

Scroll depth is a soft signal, not a conversion. A tall page scrolls more than a short one, and fast scrollers trip every threshold without reading. Use it to compare pages and spot where long content loses people, not as a success metric in its own right. Keep real conversion tracking for the outcomes that matter.

Datahound are analytics and ad-tracking specialists. We fix broken GA4, Google Tag Manager and server-side tracking so every sale, form and call gets counted. Back to datahound.agency · All tracking guides · What is event tracking?