Definition
An attribution window is the time period after a click or view within which a subsequent conversion is credited to the ad. Meta's default is 7-day click and 1-day view.
Also called: Attribution Window, Conversion windowSeveral channels can claim the same purchase.
All 100 purchases in this example are claimed by at least one channel. Adding channel reports counts shared purchases twice. MER uses store revenue and total marketing spend; it does not determine causal lift.
Why the window inflates the number
With a 7-day click / 1-day view window, Meta takes the credit if someone clicks and buys within a week, or simply sees the ad and buys within a day. View-through conversions are especially generous: many of them would have happened anyway. The wider and more inclusive the window, the more the attributed ROAS gets inflated.
Two accounts with identical results can report wildly different ROAS purely because of the window setting. And because each platform measures in its own silo with its own window, the sum of every channel's attributed revenue often exceeds the actual total.
Frequently asked questions
What's Meta's default attribution window?
7-day click and 1-day view. That means purchases within seven days of a click (or a single day after just an impression) are credited to the ad, which systematically inflates the attributed ROAS.
Which window should I use?
Pick one consistent window to compare over time, so trends are real. But never make budget decisions on the attributed number alone. Use MER and incrementality tests for the final verdict.
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