Also called: lookback window, conversion window, attribution model
Attribution windows combine with attribution models. The window decides whether a touchpoint is eligible for credit at all; the model decides how credit is divided among eligible touchpoints (last click, data-driven, position-based).
Each platform counts conversions in its own reporting, so the same sale can appear in Meta, Google Ads, and GA4 simultaneously. Summing platform-reported conversions therefore always overstates total conversions, sometimes by a large margin.
Windows shorter than the actual purchase consideration cycle systematically under-credit upper-funnel channels. If your median time-to-purchase is 18 days, a 7-day window attributes a large share of genuinely ad-driven sales to direct traffic.
Budget decisions get made on channel-reported ROAS. When windows differ across platforms and nobody reconciles them, spend shifts toward whichever platform claims credit most aggressively, not toward whichever actually drives sales.
Different attribution windows, different models, and different data sources. Meta attributes to ad interactions within its own window including view-throughs; GA4 attributes across all channels using its own model and only sees conversions its tags recorded. Discrepancies of 20–40% are normal.
Match it to your actual time-to-conversion, which you can measure in GA4's path exploration. Then keep it constant — changing windows mid-flight makes period-over-period comparisons meaningless.
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