A lookback window is the time period the platform considers when deciding whether an ad gets credit for a conversion. If a customer clicked your ad on Monday and bought on Sunday, a 7-day click-through window credits the ad; a 1-day window does not. Same conversion, different credit.
Typical settings
- Meta default after iOS 14.5: 7-day click + 1-day view
- Pre-iOS 14.5: 28-day click + 1-day view (much more generous, nicer-looking ROAS)
- Google Ads default: 30-day click for most conversion actions
- Klaviyo and email tools: usually 5-7 day lookback for attributed revenue
Why it matters
When you compare ROAS month-over-month or campaign-vs-campaign, lookback windows have to match. A campaign reporting 3.5× ROAS on a 28-day window will look more like 2.5× on a 7-day window — same business, different number. If you're benchmarking against industry data, check what window the benchmark used.
View-through vs click-through
Click-through credit applies when the user clicked your ad and later converted. View-through applies when they merely saw the ad and later converted via a different path. View-through is generous — every brand sees inflated ROAS from view-through credit. Most operators discount it heavily or report click-only ROAS as the honest number.