A conversion window, often called a lookback window, sets the maximum time between an interaction and a conversion for that interaction to receive credit. A 30-day window means a click 45 days before sign-up is ignored. Each tool sets its own windows, and a mismatch is one of the most common reasons reports disagree.
Windows in GA4
GA4 has attribution settings with separate lookback windows: one for acquisition key events (first_open and first_visit), and one for all other key events. The available options have been short choices such as 7 or 30 days for acquisition and 30, 60 or 90 days for other key events. Changing the setting applies to reports going forward and to historical data shown in attribution reports, so annotate the change.
Ad platforms
Ad platforms set windows per conversion action, often separately for clicks and views. Their defaults differ from GA4's and from each other. When comparing platform-reported conversions with GA4, line up the windows first.
Choosing a window
Match the window to how long your buyers actually take. A self-serve tool with a free plan may convert within days; an enterprise product may take months. Look at the time-to-conversion distribution in your own data, from GA4 path reports or your CRM, before picking.
- Too short: early touchpoints like content get no credit
- Too long: stale touches get credit for unrelated later decisions
- Inconsistent: tools disagree and teams argue about the numbers
Example
Two reports, two windows
Suppose Gannetforge, a contract analytics platform, sees an ad platform report twice as many conversions as GA4 credits to that platform. The ad platform uses a longer click window plus view-through credit. Aligning the windows and excluding view-through closes most of the gap, and the rest is explained by each tool's model.
Common mistakes
Never checking the default
Defaults may not suit a long B2B cycle.
Comparing tools with different windows
Align windows before arguing about which number is right.
Questions
It usually gives early touchpoints more chance of credit, but it also lets unrelated old visits claim credit. Base the window on observed buying time.
