Attribution in 2025 is messy. iOS privacy changes mean Meta sees less data. Platform-reported results don't match backend revenue. But you can still measure effectively.
Attribution Windows#
Default: 7-day click, 1-day view. This means Meta claims credit for any conversion within 7 days of a click or 1 day of viewing an ad. Compare windows to understand your customer journey.
The iOS 14.5 Impact#
Meta's reported conversions undercount by 20-40% due to iOS opt-outs. Use Conversions API to recover signal. Compare Meta reports to backend data.
MER: The Reality Check#
MER (Marketing Efficiency Ratio) = Total Revenue / Total Ad Spend. It doesn't care about attribution—it just measures efficiency. See our attribution module for setup.
