Lookback and conversion windows explained
A lookback (or conversion) window is the period before a conversion in which earlier touchpoints are eligible for credit. Touches outside the window are ignored entirely. Because every attribution model only sees touches inside this window, its length quietly governs which channels can ever receive credit.
What this means
When a conversion happens, the tool looks back over a fixed window — say 30 or 90 days — and only touchpoints inside it are candidates for credit. Anything earlier is invisible, no matter how influential it was. Platforms often have separate windows for clicks and for impressions.
Why the window dominates results
Because every model operates within the window, its length is upstream of the model choice. A short window structurally favours late, bottom-funnel touches; a long window lets discovery channels appear. Two teams running 'last-click' with different windows are not running the same analysis.
Match the window to the actual time people take to decide, write it down, and keep it stable when comparing periods.
- Touches outside the window get zero credit
- Click and impression windows can differ
- Window length can outweigh the model choice
How it appears in analytics and logs
If a channel's credit jumps when you change windows, you are seeing window sensitivity, not a real shift. Early-funnel channels live or die on a long enough window.
Diagnostic use case
Set the lookback window to match your real consideration cycle, and document it, because the same data attributed under a 7-day vs 90-day window can tell different stories.
What WebmasterID can help detect
WebmasterID makes the window an explicit, visible setting and labels confidence, so you are never comparing results across hidden, mismatched windows.
Common mistakes
- Comparing reports built on different lookback windows.
- Using a short window for a long consideration cycle.
- Forgetting impression windows differ from click windows.
Privacy and accuracy notes
Window logic operates on one site's own visitor touchpoints over time; it does not require cross-site identity. Longer windows simply mean longer first-party retention of path data.
Related pages
- First-click attribution: crediting the opener
First-click attribution assigns 100% of a conversion's credit to the very first touchpoint a visitor had. It is the mirror image of last-click: it celebrates discovery and awareness channels while ignoring everything that nurtured and closed the journey. Useful for studying acquisition, misleading as a sole budget lens.
- Attribution window vs reporting window
The attribution (lookback) window decides which past touches can earn credit for a conversion; the reporting window is the date range you are viewing. They answer different questions, and confusing them is a frequent cause of numbers that 'do not add up' between tools or between dates.
- Time-decay attribution: recent touches weigh more
Time-decay attribution weights touchpoints by recency: the closer a touch is to the conversion, the more credit it earns, usually following an exponential decay with a configurable half-life. It is a compromise between last-click and linear, but its recency bias under-credits the early demand-creating touches.
- Attribution analytics
Explicit, documented attribution windows.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.