Lookback Window

The lookback window is how far back in time GA4 looks for touchpoints when it credits a conversion. Set it to 30 days and any channel a visitor touched within 30 days before converting can earn credit. Anything older is simply ignored — invisible to attribution, no matter how important it was to the customer's decision.

Why it matters

The window quietly sets the boundary of your entire attribution story. A short window suits impulse purchases; a long one suits considered decisions that take weeks. Pick the wrong length and you'll either miss the early touchpoints that started long journeys or pad your data with stale interactions that had nothing to do with the sale.

A concrete example

A consultant's prospects typically research for six weeks before booking. With GA4's default 30-day lookback window, the organic search that first found them — eight weeks earlier — falls outside the window and gets no credit. Widen the window to 90 days and that first touch reappears, and organic search suddenly looks far more valuable than it did a moment ago.

The common misreading

People read a channel's conversion count as fixed truth when it's partly an artifact of the window length. Shorten the window and early-funnel channels seem to collapse overnight, even though nothing about them changed. Before concluding a discovery channel stopped working, check whether the lookback window was narrowed underneath the report.