Summary
Use the Session primary channel group dimension to determine whether website traffic is coming from organic search, referral or another source. It is the default dimension in the Traffic acquisition report and groups every session into a named channel based on its source and medium values. Switch to Session source/medium when you need the underlying detail.
Nitin Batra is a Google certified digital marketing professional who works with GA4 acquisition reporting, channel grouping and UTM tagging frameworks for client accounts on a daily basis.
Last updated: August 16, 2026
- The Campaigns section within the Reports workspace
- The Advertising workspace
- The Admin workspace
- The Explore workspace
The correct answer is: The Advertising workspace
Key Takeaways
- – Session primary channel group is the correct dimension for identifying whether traffic came from organic search, referral, direct, paid or other channels.
- – It is the default primary dimension in the Traffic acquisition report, and the dropdown lets you swap to Session source, Session medium or Session campaign for finer detail.
- – Channel groups are rules applied to the source and medium values collected with each session, so accurate UTM tagging directly controls how clean your channel reporting looks.
- – Do not mix session scope with user scope. First user primary channel group reports the channel that first brought the person to the site, while Session primary channel group reports the channel for each individual visit.
Where exactly do I find Session primary channel group in GA4?
Open Reports, go to Acquisition and click Traffic acquisition. The table loads with Session primary channel group as the first column by default. You can also pick it from the dimension dropdown just above the table, or add it as a dimension inside any Exploration.
What is the difference between Traffic acquisition and User acquisition reports?
Traffic acquisition uses session scoped dimensions and answers the question of which channel brought each visit. User acquisition uses first user scoped dimensions and answers which channel first brought that person to your site. Use Traffic acquisition for campaign and channel performance, and User acquisition when you want to judge which channel is best at finding new users.
Why does so much of my traffic show up as Unassigned or Direct?
Unassigned means the source and medium values collected did not match any channel definition rule, usually because of a badly formed or non standard utm_medium. Direct means no referrer information was passed at all, which happens with untagged email links, app clicks, PDFs and some browser privacy settings. Fixing your UTM tagging removes most of both problems.
Can I change how GA4 assigns traffic to channels?
Yes. In Admin, under Data display, open Channel groups and create a custom channel group with your own rules based on source, medium and campaign. Custom channel groups apply retroactively in most reports, so you can reclassify historic traffic without re tagging it, though the default channel group stays available alongside it.
1 Views