GA4 default channel group: the rules, and how to build your own

What a channel group is in GA4

A channel is a named bucket for traffic sources. A channel group is the set of rules that fills the buckets. GA4 ships with one, the default channel group, and Google maintains it: “It’s not possible to edit the Google Analytics default channel group because Google maintains a universal default for all users” (Google Analytics Help, checked October 2026).

The same channels appear in three dimensions, and they answer different questions:

Session and first user dimensions use paid and organic last click. The event-scoped one uses the attribution model set for the property, which is data-driven by default. Three reports can show three different numbers for “Email” and all be correct, because they are not the same dimension.

GA4 also has a primary channel group. It starts as a copy of the default and, unlike the default, can be edited. It is the one to change if you want your own definitions to appear in standard reports.

The default channel rules for tagged traffic

For traffic from Google Ads, Display & Video 360 and the other linked Google products, GA4 reads the channel from the integration. For everything else, the channel follows from the source, medium and campaign name, which means from your UTM tags. These are the rules from Google’s table:

The paid pattern is the regular expression ^(.*cp.*|ppc|retargeting|paid.*)$. A medium of cpc, cpm, ppc, paid or paid_social matches. A medium of ads or sponsored does not.

The lists of search, social, video and shopping sites are Google’s own; the Help page links a spreadsheet with them.

Two rules are newer than most guides. AI Assistant is its own channel: GA4 sets the medium to ai-assistant when the referrer matches Google’s list of AI assistants. And Cross-network covers Performance Max, Demand Gen and Smart Shopping campaigns.

Why traffic lands in Unassigned

Google’s definition: “Unassigned is the value Analytics uses when there are no other channel rules that match the event data.” In practice there are three reasons.

• The medium is one GA4 does not know. utm_medium=newsletter is not email by the rules above. utm_medium=fb_ads is not paid. Both go to Unassigned.
• A paid medium with an unknown source falls to Paid Other, not Paid Social. utm_source=meta&utm_medium=cpc works only if meta is on Google’s list of social sites.
• The source is missing. A session with (not set) as source and medium matches nothing. The causes are covered in what (not set) means in GA4.

The fix for the first two is in your links, not in GA4: use the medium values from the table. A tagging scheme and a builder are covered in the guide to UTM tags.

The same source can also be split in ways the channel group hides. One social network arrives as several referrers:

How to see channels in GA4 reports

Open Reports, Acquisition, Traffic acquisition. The table is grouped by Session default channel group, or by Session primary channel group once you have set a custom group as primary. Use the drop-down above the first column to switch to Session source / medium or Session campaign, and the plus sign to add a second dimension.

For first-touch channels, open User acquisition, which uses First user default channel group.

How to create a custom channel group

A custom channel group is your own rule set. It works next to the default and applies to historical data in reports, so you can compare old and new definitions on the same date range.

1. Open Admin, then Data display, then Channel groups.
2. Click Create new channel group. To start from Google’s rules instead of an empty list, use Copy to create new on the default group.
3. Give the group a name and a description.

4. Click Add new channel, name it, and add conditions on source, medium, campaign or the other traffic dimensions.
5. Use Reorder to set the order. Rules are evaluated from top to bottom and the first match wins, so put narrow channels above broad ones.
6. Click Save group.

The group then appears as a dimension in the acquisition reports and in explorations.

Where GA4 channel groups stop

Custom channel groups solve naming. They leave four things open:

• The default cannot be changed, and many shared reports and integrations use it.
• Rules can only use the dimensions GA4 offers. A channel that depends on your own data, such as a partner list, a campaign plan or a CRM field, cannot be expressed.
• Costs are not there. GA4 has spend for linked Google Ads accounts. For other platforms it has only what you import by hand.
• The definition lives in one property’s Admin. The dashboard, the finance sheet and the warehouse each need their own copy, and copies drift.

There is a fifth, and it surprises people when they link BigQuery: the default channel group is not a field in the export. The export gives you source, medium and campaign. The channel is yours to define.

Define channels in BigQuery

In the warehouse a channel group is a CASE expression. This one follows Google’s rules for a few channels and runs as written on the public GA4 sample:

SELECT
  CASE
    WHEN traffic_source.source = '(direct)'
      AND traffic_source.medium
        IN ('(none)', '(not set)')
      THEN 'Direct'
    WHEN REGEXP_CONTAINS(
      traffic_source.medium,
      r'^(.*cp.*|ppc|retargeting|paid.*)$')
      THEN 'Paid'
    WHEN traffic_source.medium = 'organic'
      THEN 'Organic Search'
    WHEN traffic_source.medium
        IN ('referral', 'app', 'link')
      THEN 'Referral'
    WHEN REGEXP_CONTAINS(
      traffic_source.medium, r'^(e[-_ ]?mail)$')
      THEN 'Email'
    WHEN traffic_source.medium = 'affiliate'
      THEN 'Affiliates'
    ELSE 'Unassigned'
  END AS first_user_channel,
  COUNT(DISTINCT user_pseudo_id) AS users
FROM
  `bigquery-public-data.ga4_obfuscated_sample_ecommerce.events_*`
WHERE _TABLE_SUFFIX BETWEEN '20210101' AND '20210131'
GROUP BY first_user_channel
ORDER BY users DESC

traffic_source is the user’s first source, so this is the equivalent of First user default channel group. Unassigned is large here because Google replaced part of the sample’s sources with placeholder values. On your own export, a large Unassigned row is the list of mediums your tagging scheme has to cover.

The point of doing it in SQL is that the rules are now yours. You can add a line for your affiliate network, read a mapping table maintained by the marketing team, or join spend from the ad platforms by campaign. Linking a property is covered in connecting GA4 to BigQuery.

One channel definition for every report

A CASE expression pasted into five queries is five definitions. The marketer’s version of the problem is familiar: the weekly report says Paid Social brought 400 sessions, the dashboard says 520, and both were built by careful people.

OWOX Data Marts keeps the definition in one place. An analyst writes the channel logic once, saves it as a Data Mart on the warehouse that holds the export, and publishes it with a description of each channel. Reports for Google Sheets and Data Studio (the former Looker Studio) are built on that Data Mart, so a change to the rule reaches all of them.

OWOX Data Marts does not decide what a channel is and does not collect GA4 data. The rules are the analyst’s SQL, on tables already in your warehouse. What the product adds is that marketers work with the published result in a spreadsheet, without editing the logic. Because ad platforms such as Facebook Ads, TikTok Ads and Microsoft Ads are available as data sources, spend can sit in the same warehouse and be joined by campaign, as shown in blending GA4 conversions with ad spend.

GA4GA4 Data API limits and quotas, and when to use BigQueryOctober 7, 2026→GA4How to set up GA4 tags with Google Tag ManagerSeptember 12, 2023→GA4GA4 Measurement Protocol: what it is and how to use itOctober 3, 2023→

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