How to Check UTM Performance in GA4: Reading Source/Medium and Campaign Reports
Once you have tagged your links carefully, it is time to read the results in Google Analytics 4 (GA4). GA4's layout differs from the previous version, so it is easy to get lost at first. This guide covers where and how to see UTM traffic in GA4, and what to check when values do not show up correctly.
Where to look: the Traffic acquisition report
The first place to look is Reports → Acquisition → Traffic acquisition. This report shows traffic by session. The first column defaults to "Session default channel group"; open its dropdown and switch dimensions to see UTM values directly.
- Session source / medium — shows utm_source and utm_medium joined, like naver / cpc or newsletter / email. The most-used view.
- Session campaign — performance by utm_campaign. This is where good campaign names pay off.
- Session source, Session medium — view each separately.
On the right, the table shows sessions, engaged sessions, engagement rate, and conversions (key events), so you can compare which UTM combination actually performed.
How the default channel group relates to medium
The "default channel group" (Paid Search, Email, etc.) on GA4's first screen is actually an automatic classification based on the utm_medium value you entered. That is why standardizing medium matters so much.
| utm_medium value | GA4 channel |
|---|---|
| cpc, ppc, paid | Paid Search |
| display, banner | Display |
| paid-social | Paid Social |
| social | Organic Social |
| affiliate | Affiliates |
If you put a non-standard value like facebook_ad in medium, GA4 cannot place it in any channel and marks it Unassigned. A large Unassigned share almost always means your UTM medium values are off-standard.
Connecting to conversions
Session counts alone are only half the picture. What you really want is "which campaign drove revenue (or signups, or inquiries)." In GA4 you can mark actions like purchase, signup, or add-to-cart as key events (conversions). With conversions set, the Traffic acquisition report shows conversions and revenue per campaign on the right, so you can read channel- and campaign-level results like "the Naver search-ad summer sale campaign drove 30 conversions and 1.2M KRW."
Going deeper: Explore
When standard reports are not enough, Explore lets you freely combine dimensions and metrics. Put "Session campaign" and "Session source/medium" in rows and conversions/revenue in columns, and you can drill into which source drove conversions within a campaign. You can also build creative-level comparisons split by utm_content here.
Checklist for when UTMs do not show up
If you tagged carefully but see nothing in GA4, it is usually one of these.
First, standard reports take hours to a day to process. If you just tested, check Reports → Realtime.
Second, parameters may have been lost through a redirect. Short URLs or ad-platform hops can strip UTMs, so confirm the parameters remain in the final page's address bar.
Third, the self-referral problem. If you tagged internal links, or a session breaks while visiting an external domain for payment or login, the original source disappears. Only tag external inbound links, and add payment domains to the referral exclusion list.
Fourth, values split by case or typos. If Google and google appear on two rows, they were not standardized. Forced lowercase and templates prevent this at the root.
Summary
In GA4, read UTM performance in the Traffic acquisition report by source/medium and campaign, and set conversions to connect it all the way to revenue. The default channel group is auto-classified by your standard medium values, so a clean report ultimately comes down to the rules you follow when building links. Good analysis starts with good tagging.