Measurement
Attribution window
An attribution window is the period after an ad interaction during which a resulting conversion is still credited to that interaction.
Window length changes reported performance without changing reality. A 7-day-click window and a 28-day-click window describe the same campaign and produce materially different ROAS, which is why comparing numbers across platforms or across time without checking the window is a common and expensive error.
Longer windows credit more conversions and are more likely to capture ones that would have happened anyway — so a generous window and a weak incrementality result frequently describe the same campaign.