Scroll depth tracks how far users scroll on a given page. It's commonly reported at percentage milestones — 25%, 50%, 75%, and 100% — or as an average scroll percentage across all sessions.
Why Scroll Depth Matters for CRO
Most CRO focuses on clicks and conversions, but scroll depth answers a prior question: did users even see the thing you're trying to optimize?
If your primary CTA sits 60% down the page and 70% of users never scroll past 40%, the button's design is irrelevant — visibility is the real problem.
Common insights from scroll depth analysis:
| Finding | Likely action |
|---|---|
| Drop-off at 30% on long-form landing page | Move key value proposition or CTA higher |
| Users rarely reach pricing section | Restructure page to surface pricing earlier |
| High scroll on blog posts but low CTR on inline CTAs | Reposition CTAs to where engagement peaks |
| Mobile scroll depth much lower than desktop | Prioritize content visible above the fold on mobile |
Measuring Scroll Depth
Scroll depth is typically captured via:
- Analytics platforms — Google Analytics 4 natively tracks scroll depth as an event (90% scroll threshold by default; configurable)
- Heatmap tools — Hotjar, Clarity, FullStory visualize scroll depth as an overlay showing the percentage of sessions reaching each vertical point
- Custom event tracking — Fire events at custom thresholds (e.g., every 10%) for more granular analysis
Scroll Depth vs. Time on Page
Time on page and scroll depth measure related but distinct behaviors. A user can spend 5 minutes on a page without scrolling (reading a dense introduction), or scroll quickly to 100% without reading at all. Use both together for a fuller picture of engagement.
Using Scroll Depth in A/B Tests
Scroll depth is most useful as a diagnostic metric, not a primary success metric. Use it to:
- Identify page structure problems before running conversion tests
- Validate that users in a variant are reaching critical content
- Explain unexpected results — if a variant lifts clicks on a bottom-of-page CTA, check whether scroll depth also improved