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Avg. Max Scroll Depth is the average, across sessions, of the deepest scroll position each session reached on any one page. A session that scrolled 40% of the homepage and 90% of a product page counts as 90%.

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Formula

Avg. Max Scroll Depth = SUM ( deepest scroll % per session ) ÷ Number of sessions
Session metrics are calculated from Upstack’s session records. They aren’t offered in the dashboard metric picker.

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How the Upstack Pixel measures scroll depth

On every page, the Upstack Pixel samples the scroll position once per animation frame while the visitor scrolls and calculates:
It rounds the result and caps it at 100. The pixel keeps the highest value seen on the page and sends it with heartbeats and when the visitor leaves the page. The session record keeps the highest value across all pages in the session. What this means in practice:
  • 100% means the bottom of the page reached the bottom of the window, not that the visitor looked at every element.
  • A page shorter than the window scores 0%. There’s nothing to scroll, so the scrollable distance is zero. Short pages pull the average down even when visitors saw everything.
  • The session value is a maximum, not an average of pages. One deep scroll on one page sets it.
Every session counts in the denominator, including sessions that never scrolled.

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Worked example

Four sessions on an outdoor-gear store: Avg. Max Scroll Depth = (85 + 100 + 0 + 60) ÷ 4 = 61.25%. Session C saw the whole size guide, but it scores 0 because the page couldn’t scroll. Without it, the average would be 81.67%.

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How to interpret it

  • Compare like with like. Group by landing page before comparing. Long editorial pages and short product pages produce very different depths for the same interest level.
  • A drop after a redesign may only mean the page got longer. Check whether the content you care about moved further down.
  • Pair it with active time. Deep scroll with little active time suggests skimming. Moderate scroll with long active time suggests reading.
  • It feeds other scores. Deep scroll (75% or more) is one of the intent signals on the session, and scroll depth below 25% is part of the Bounce Rate (No Interaction) rule.

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FAQ

Pages that fit inside the browser window can’t be scrolled and record 0%. Sessions that only see short pages pull the average down.
Both. The pixel tracks the deepest scroll per page, and the session keeps the highest page value. This metric averages the session values.
No. The pixel reads only the vertical scroll position.
See all Session metrics →