Definition
What is Attribution Model?
An attribution model is the set of rules that decides how credit for a conversion is assigned across the touchpoints a user interacted with before converting. Common models include last-click, first-click, and data-driven attribution, which GA4 uses by default. The chosen model changes which channels appear to drive results.
Why it matters
The attribution model directly shapes budget decisions, because it determines whether organic search, paid ads, or another channel gets credit for the conversions they influenced.