Attribution Model

An attribution model is the rule GA4 uses to decide which marketing channel gets credit when someone converts after touching more than one. If a visitor finds you through search, comes back later from an email, then converts, the attribution model determines whether search, email, or both earn the conversion. GA4's default is data-driven attribution, which splits credit based on patterns in your own data.

Why it matters

The model you use silently shapes every decision you make about where your customers come from. Last-click attribution hands all the credit to the final touchpoint, which tends to flatter whatever channel closes the sale and starve the ones that started the journey. Change the model and the same conversions get reassigned — no behaviour changed, but your report tells a different story.

A concrete example

Suppose you run paid ads to attract first-time visitors and email to bring them back to buy. Under last-click, email looks like your hero channel and the ads look wasteful. Switch to data-driven attribution and the ads suddenly get partial credit for sparking the journey. If you'd cut ad spend based on the last-click view, you'd have been cutting the channel that fed the whole funnel.

The common misreading

The most damaging mistake is treating a drop in a channel's conversions as a performance problem when the attribution model was quietly changed. Conversions that fell off a cliff after a model switch didn't disappear — they were reassigned. Before you conclude a channel stopped working, check whether the model or the lookback window changed underneath you.