Channel Group Checker for GA4: Default Grouping Rules and Unassigned Traffic

How to find the cause of GA4 unassigned traffic

Most GA4 unassigned traffic comes from UTM tags that don't fit Google's channel rules. This checker runs your link, or your whole report, through the same 19 rules, in the same order, that Google publishes on its [GA4] Default channel group page. It tells you which rule matched — or why none did — and what to change.

1. Choose what to check. One link, a source and medium you type in, or many rows at once.
2. Paste your link. The tool reads utm_source, utm_medium and utm_campaign, and spots Google Ads click IDs.
3. Read the verdict. You see the channel, the rule number and the reason, such as “source fb_ads is not on Google's list of social sites”. The table shows every rule GA4 tests before it stops.
4. Apply the fix. For Unassigned and Paid Other results you get values that land in a named channel, plus a fixed link to copy.
5. Check a whole report. In GA4, export Traffic acquisition with “Session source / medium”, then paste it under Many rows. With a Sessions column, the tool shows how many sessions each problem costs you.

What to do next

1. Fix the tags where they are made. Change the URL parameters in the ad platform, your email tool's UTM settings or your link sheet. GA4 reads the tags at the moment of the visit.
2. Watch the new data. In GA4, open Reports › Acquisition › Traffic acquisition with “Session source / medium” and check the new rows.
3. Regroup past data if needed. The default group can't be edited, but a custom channel group (Admin › Data display › Channel groups) also applies to past reports.
4. Write the rules down. One agreed list of sources and mediums stops the problem coming back.

Why GA4 traffic is unassigned: causes and fixes

A medium no rule knows

Values like social_paid, sponsored, boosted_post, qr or print match nothing. Paid traffic needs a medium that starts with “paid”, contains “cp”, or is ppc or retargeting. Organic links need one of Google's exact words, such as social, email, referral or affiliate.

GA4 unassigned (not set): the medium is missing

Without utm_medium the medium is (not set). Only a source a rule knows on its own still matches — a listed site like google, or email and sms. newsletter alone is Unassigned.

A source nickname instead of the listed name

meta, fb_ads, msads and google.com are not on Google's lists. With a paid medium they fall into Paid Other; with a medium like post or story they end up Unassigned. Use the listed name: facebook, bing, google.

Paid social traffic shows as Paid Shopping

Paid Shopping is tested before Paid Social and reads the campaign name: “summer_shop_sale” on a Facebook ad lands in Paid Shopping. “cross-network” in a name beats every rule but Direct.

AI Assistant visits

Since May 2026 GA4 sets the medium to ai-assistant itself for assistants it recognizes. The list isn't published, so a hand-made chatgpt.com / referral stays in Referral.

GA4 default channel grouping rules, in order

GA4 tests these from top to bottom, ignores capital letters and stops at the first match. The paid pattern is ^(.*cp.*|ppc|retargeting|paid.*)$; the shop pattern ^(.*(([^a-df-z]|^)shop|shopping).*)$ matches “eshop” and “summer_shop” but not “workshop”. Google doesn't say if its site lists match whole values, so this tool matches whole values — use google, not google.com, which isn't listed.