Summary
Dimensions without a scope prefix, for example Source and Medium, will reflect the new Data-driven attribution setting. These attribution scoped dimensions carry key event credit, so changing the model redistributes conversions across them. First user and Session prefixed dimensions record fixed historical facts and stay unchanged.
Nitin Batra is a Google Analytics 4 certified professional who configures attribution settings and builds model comparison reports for client properties as part of his daily analytics work.
Last updated: August 16, 2026
When you switch the attribution model from Last click to Data-driven in GA4, only the dimensions without a scope prefix, such as Source, Medium and Campaign, reflect the new attribution setting.
- Dimensions with the First user prefix (e.g., First user source)
- Dimensions with the Session prefix (e.g., Session source)
- Dimensions related to Google Ads campaigns only (e.g., Google Ads campaign)
- Dimensions without a scope prefix (e.g., Source, Medium)
The correct answer is: Dimensions without a scope prefix (e.g., Source, Medium)
Key Takeaways
- – Dimensions without a scope prefix, such as Source, Medium and Campaign, are the ones that reflect a change from Last click to Data-driven attribution.
- – The attribution model only redistributes key event and revenue credit, it does not change session counts, user counts or traffic volume in any report.
- – GA4 has three traffic scopes: user scope with the First user prefix, session scope with the Session prefix, and attribution scope with no prefix at all.
- – A common mistake is expecting Session source or First user source numbers to move after switching models. They never do, because those dimensions record what actually happened rather than assigned credit.
Where do I change the attribution model in GA4?
Go to Admin, then under Data display open Attribution settings. There you pick the reporting attribution model and the lookback window for acquisition and other key events. The change applies retroactively to historical data, so your past conversion credit is recalculated as well.
What is the difference between First user source, Session source and Source in GA4?
First user source is user scoped and stores the source that first brought that user to your site, and it never changes. Session source is session scoped and records how each individual session started. Source with no prefix is attribution scoped, and it is the one that reflects whichever attribution model you have selected.
Does switching to Data-driven attribution change my traffic numbers?
No. Users, sessions and engaged sessions stay exactly the same. Only the way key events and their revenue are credited across channels changes, so you may see paid search or display gaining credit while direct or last-touch channels lose some.
Why does Google Analytics 4 use Data-driven attribution as the default now?
Last click gave all the credit to the final touchpoint, which undervalued upper funnel channels like display, video and paid social. Data-driven attribution uses your own property’s conversion paths to work out how much each touchpoint actually contributed. It needs a reasonable volume of conversion data to build the model, and Google Ads conversion values in GA4 follow the same logic.