Attribution models and conversion paths

Attribution is the rule for splitting credit for a key event among the touchpoints before it. GA4 offers two families (Admin > Attribution settings):

• Data-driven (default since 2023): a model trained on your property's paths that assigns fractional credit based on how much each touchpoint changed the probability of converting. It needs enough data; small properties fall back to last click.
• Paid and organic last click: 100% to the last non-direct touchpoint.
• Google paid channels last click: 100% to the last Google Ads click if there is one, else last non-direct click. Mainly for comparing with Google Ads' own reporting.

First-click, linear, time-decay and position-based were removed in 2023.

Lookback window controls how far back touchpoints count: acquisition key events (first_open, first_visit) 7 or 30 days; all other key events 30, 60 or 90 days. Changing the model or window re-attributes historical data in reports, but not in already-exported BigQuery tables.

The choice of dimension scope matters as much as the model. Session source / medium credits the session in which the key event happened, regardless of model. First user source credits the first ever visit. The attribution model only applies to attribution-scoped dimensions, which are the plain Source, Medium, Campaign and Default channel group you find in the Advertising section and in Explore under Attribution; use those with Key events or Total revenue to see model-based credit.

The Advertising section (left nav) holds the attribution reports: Model comparison (same key event under two models side by side, with % change per channel), Key event paths (sequences of touchpoints, their count, days and touchpoints to key event, split into early/mid/late), and Attribution overview. Set the key event filter at the top of each report; the default is all key events combined.

A channel that gains credit under data-driven but loses under last click is an assisting channel: it introduces people who convert later via something else.