Summary
First user source will display Paid Search. The sponsored search click was the first touchpoint that introduced this user to the site, and user-scoped dimensions keep that value permanently. The email click only affects session-scoped dimensions for that second session.
Nitin Batra is a Google Analytics 4 certified professional who configures acquisition reporting, attribution settings and user-scoped versus session-scoped dimensions in live GA4 properties.
Last updated: August 16, 2026
In this scenario the First user source dimension will display Paid Search, because user-scoped acquisition dimensions permanently record the sponsored search click that brought the user to the site for the very first time.
- Organic Search
- Paid Search
- (not set)
The correct answer is: Paid Search
Key Takeaways
- – First user source will display Paid Search, because that is the channel that brought the user to the site on their very first visit.
- – First user dimensions are user-scoped and written once at first identification, so later sessions cannot overwrite them.
- – Session-scoped dimensions such as Session source and Session primary channel group update with every new session, which is why the same user can show Email for the second visit.
- – A common mistake is comparing First user metrics with Session metrics in the same table. Also remember that if the user clears cookies or switches device without signing in, GA4 treats them as a brand new user and rewrites the first user source.
What is the difference between First user source and Session source in GA4?
First user source is user-scoped and records the source that brought a person to the site for the first time. Session source is session-scoped and records the source that started each individual visit. A single user can therefore have one First user source and many different Session sources over time.
Which GA4 report uses First user source by default?
The User acquisition report under Reports, Life cycle, Acquisition uses First user dimensions such as First user primary channel group, First user source and First user medium. The Traffic acquisition report sitting right below it uses Session dimensions. Switching between the two is the fastest way to see whether a channel is acquiring new users or re-engaging existing ones.
Why does the email campaign not overwrite the First user source value?
Because GA4 writes user-scoped acquisition data only once, at the point the user is first seen. Any later campaign, referral or direct visit updates session-scoped fields instead. This design exists so you can measure true acquisition performance without later touchpoints hiding the channel that originally found the customer.
Can First user source ever change for the same person?
Yes, but only when GA4 stops recognising the person as the same user. If they clear browser cookies, use a private window, switch to another browser or device without a User ID, GA4 counts them as a new user and stamps a fresh First user source. Setting up User ID with a logged in audience reduces how often this happens.