Lookback Window

The lookback window is the span of time before a conversion during which earlier touchpoints are eligible to receive credit.

Any touchpoint older than the window is treated as if it never happened for attribution purposes. GA4 lets you set this for acquisition conversions, with the default running back a set number of days before the conversion. Touchpoints inside the window compete for credit under whatever model you have chosen, anything outside it is dropped.

Set the window to 30 days and a user first clicks your ad on day one but does not convert until day forty. That first click falls outside the window, so it gets no credit even though it started the journey. Widen the window and the same first click becomes eligible again.

A short window flatters your closers and hides long sales cycles. If your buyers research for months, a tight lookback window will credit only the recent touches and make your early-funnel work invisible. Match the window to how long people actually take to buy, not to whatever the default happens to be.

Set the window too short and half the journey disappears.