Attribution Window
An attribution window is the period after an ad interaction during which a conversion is credited to that ad — e.g. 7-day click.
Attribution windows define how long after someone clicks or views your ad the platform will count a subsequent conversion as being "caused" by that ad. The default on Meta is 7-day click + 1-day view; on Google it varies by campaign type.
Shorter windows are more conservative and under-count conversions (because some buyers take longer to decide). Longer windows credit more conversions to ads but risk over-counting by including purchases that would have happened anyway.
Post-iOS 14.5, attribution became a major pain point. Platform-reported ROAS and CPA rely on these windows and are only as accurate as the tracking allows. Many advertisers now supplement platform attribution with server-side tracking, post-purchase surveys and blended MER.
Related terms
ROAS
ROAS is the revenue earned for every dollar spent on advertising, expressed as a multiple (4x means $4 back per $1 spent).
CPA
CPA is the average advertising cost to acquire one customer or conversion, calculated as total ad spend divided by total conversions.
MER
MER is total revenue divided by total marketing spend across all channels, giving a blended view of marketing efficiency.
Retargeting
Retargeting shows ads to people who already interacted with your brand — site visitors, product viewers, cart abandoners — to bring them back.