lookback window

GA4 does not use one universal number. Acquisition key events (first_open and first_visit) default to a 30-day window, adjustable down to 7. Every other key event, including purchases and form submissions, defaults to 90 days, with 30 or 60 as options. Engaged-view events sit at a fixed 3 days.

Why the window comes before the model

The window you pick applies to every attribution model at once, so switching from last-click to data-driven does not change which touchpoints are even in the running. The window already drew that boundary. A worked example: with the 90-day default, a purchase on March 31 can credit any tracked click back to January 1. A visit from January’s organic search result stays eligible. A click from the prior October does not, because it fell outside the window.

Two behaviors trip people up. First, changes are not retroactive. They apply going forward, so historical reports keep their old boundary. Second, direction matters. Shortening the window takes effect right away, while lengthening it fills in gradually as new data accrues. Shorter windows understate long consideration cycles. Longer windows capture slow B2B journeys but blur which recent touch actually moved the deal. There is no neutral setting, only a trade you should make on purpose rather than by accident.