An attribution window is the defined period after an ad interaction, a click or a view, during which a subsequent conversion is credited to that ad. Meta’s default attribution setting is a 7-day click and 1-day view window, meaning any purchase within 7 days of a click or 1 day of a view is attributed to that campaign. Changing the attribution window significantly affects reported ROAS and conversion numbers, a 28-day window will show far more attributed conversions than a 1-day window for the same campaign. Advertisers comparing Meta performance to other channels must align attribution windows to avoid double-counting.