How it works
Each engagement type has its own window. Click windows are counted by the day; seven days is a common setting and many tools allow up to thirty. View-through windows are much shorter, typically 24 hours or less, because an impression is weaker evidence than a click. When the app is first opened, the measurement platform looks back from that moment and considers only engagements that are still inside their window. Self-attributing networks apply their own windows, and Apple sets the windows that SKAdNetwork uses.
Why it matters for an app team
The window decides how many installs count as paid. A long window credits more installs to campaigns, including some that would have happened anyway; a short one moves installs to organic. Agreeing windows with each partner up front avoids arguments over invoices.
In practice
Example: with a 7-day click window, a user who taps an ad on day 1 and opens the app on day 6 is attributed to that ad. If the same user first opens the app on day 10, the install is organic.
Common confusion
The window is counted to the first app open, not to the store download, because the SDK only learns about an install when the app runs. It is also separate from the cohort period (day 7, day 30) used to measure what users do after installing, and from the re-engagement window used for existing users.