traffic acquisition

GA4 splits acquisition into two reports, and the difference trips people up. Traffic acquisition is scoped to sessions, so it answers “which channel drove this visit.” User acquisition is scoped to new users and reports the first source that ever brought someone in. Same metric names, different denominators, so the numbers will not match. Google’s own docs tell you not to compare them directly.

What the report shows

The default dimension is Session default channel grouping, a rule-based set of buckets: Organic Search, Paid Search, Direct, Referral, Organic Social, Email, and more. Against each channel you get sessions, engaged sessions, engagement rate, average engagement time, key events, and total revenue. You can swap the dimension to Session source / medium for finer detail, or type google / organic into the table search to isolate organic Google traffic.

For SEO, the Organic Search row is the one that matters. Its session trend tells you whether search traffic is growing, flat, or leaking, and its engagement rate tells you whether that traffic actually sticks. Because the report is session-scoped, a returning organic visitor is counted every time they come back through search, not only on their first visit. That makes it the right lens for judging ongoing organic performance rather than one-time discovery.