GA4 Default and Custom Channel Groups

This guide uses Analytics Help: Default channel group, Custom channel groups, Scopes of traffic-source dimensions, Understand (direct) / (none) traffic, Identify unwanted referrals and What's new in Google Analytics. Quotes are from those pages.

What a channel group is

Google describes channels as "rule-based definitions of your website's traffic sources". A channel group is a set of those channels. Every GA4 property gets the same default channel group, maintained by Google, with channels such as Organic Search, Paid Social, Email and Referral. Each visit or key event is put in the first channel whose rules it matches; if none match, it is reported as Unassigned.

You cannot edit the default group. Google gives the reason: it "maintains a universal default for all users that can be kept current, accurate, and serve as a reference for the life of every property." What you can do is build your own custom channel groups and choose one of them as the property's primary channel group. Both are covered below.

The rules mostly read the source, medium and campaign of a visit. Setting those correctly on your own links is the job of UTM tags, which we cover separately in our UTM tracking links guide, including the mediums that put tagged visits in the right channel. This guide is about the groups themselves.

Three channel dimensions, three scopes

The default channels show up as values of three different dimensions, and they can disagree with each other on purpose:

Dimension	What it describes	Attribution	Scope
Default channel group	The channels by which users arrived and triggered a key event	The property's attribution model (data-driven by default)	Event
Session default channel group	The channels by which users arrived when they started a new session	Paid and organic channels last click	Session
First user default channel group	The channels by which users first arrived	Paid and organic channels last click	User

So the Traffic acquisition report (sessions) and the User acquisition report (new users) can show different channel totals for the same date range, and both can differ from key event credit in the Advertising section. Google notes that event-scoped source and medium are "(not set)" for events that are not key events. How the attribution model shares credit is in our GA4 attribution guide.

The default channels

Google's default group has these channels. The descriptions are shortened from Google's table:

• Direct: a saved link or a typed URL.
• Organic Search: non-ad links in search results, including Google's AI Overviews and AI Mode.
• AI Assistant: sources like ChatGPT, Gemini, Deepseek, Copilot or Grok. It excludes AI Overviews and AI Mode, which stay in Organic Search.
• Organic Social, Organic Video, Organic Shopping: non-ad links on social, video and shopping sites.
• Paid Search, Paid Social, Paid Video, Paid Shopping: ads on search, social, video and shopping sites.
• Display: display ads, including the Google Display Network.
• Cross-network: ads that run across several networks, such as Search and Display.
• Paid Other: ads not identified as Search, Social, Shopping or Video.
• Referral: non-ad links on other sites or apps, such as blogs and news sites.
• Email, SMS, Mobile Push Notifications, Affiliates, Audio: links in email and text messages, push notifications, affiliate sites and audio ads.

The AI Assistant channel is recent. Google's What's new page dates it to May 13, 2026: when the referrer matches a recognised AI assistant, GA4 sets the medium to "ai-assistant" and the campaign to "(ai-assistant)". So when you compare months, keep that date in mind.

Which sites count as "search", "social", "video" or "shopping" comes from a list Google keeps; the Default channel group article links to it as a downloadable spreadsheet. Google says the definitions "may evolve as the market changes", are not case sensitive and cannot be edited. Site owners can ask to be added to the list at the address Google gives on that page; Google says it reviews requests "at least once per year".

How ad platform traffic is sorted

Traffic from Google's own ad platforms is not sorted by UTM tags. For Google Ads, GA4 uses the source platform plus the ad network type, and the campaign type for Paid Shopping. A few of the rules Google lists:

• Shopping campaigns go to Paid Shopping.
• Google Search and Search Partners traffic, and Search, Hotel and Travel campaigns, go to Paid Search.
• YouTube traffic and Video campaigns go to Paid Video.
• Performance Max, App, Smart, Demand Gen and Local campaigns go to Cross-network.
• Traffic identified with the GBRAID parameter is sorted by campaign type.

Display & Video 360 and Campaign Manager 360 traffic is sorted by creative format, Search Ads 360 traffic from other engines by engine account type, and Merchant Center free listings go to Organic Shopping. Everything else, including ads you run on other platforms, falls under the "manual traffic" rules, which read your source, medium and campaign name.

One consequence: for manual traffic, Cross-network is matched when the campaign name contains "cross-network". A campaign name that happens to include those words can move traffic out of the channel you expected.

Unassigned, (other) and Direct

Google defines Unassigned as "the value Analytics uses when there are no other channel rules that match the event data." In practice that is usually a link tagged with a medium no rule recognises. The fix is in the tagging, not in the channel group, though a custom group can catch a medium you cannot change.

(other) is a different thing: an aggregated row GA4 shows when a report hits its cardinality limits. It does not mean the rules failed.

Direct means the source is "(direct)" and the medium "(none)" or "(not set)". Google's (direct) / (none) article lists the usual reasons:

• Links without UTM parameters, or a site that isn't linked to its ad platforms.
• Redirects, including from https to http, that strip the parameters, and URL shorteners that remove referral details.
• People typing the URL, or clicking links in PDFs and Word documents.
• Ad blockers that interfere with the cookies used to identify where traffic came from.

Payment pages and other third-party domains in the checkout path can show up as Referral sources. Google's answer is the unwanted referrals list in the web stream's tag settings, up to 50 conditions per data stream.

Custom channel groups

A custom channel group is your own copy of the rules, with channels renamed, added, removed or reordered. Custom groups can use these fields: campaign ID, campaign name, default channel group, manual ad content, medium, source and source platform.

Limit	Standard property	Analytics 360 property
Custom channel groups	2, plus the default group	5, plus the default group
Channels in each group	50	50

Where you can use them:

• As the primary dimension in reports that already support the default channel group, such as the Acquisition reports.
• As a secondary dimension in default reports, such as the Events report.
• In custom reports, explorations and audience conditions.

Google states that custom channel groups "can be applied to your reports retroactively", so a group created today also sorts last year's data. The exceptions Google lists: custom groups are not available in the key events paths report, cost, click and impression figures are not available for the manual ad content field, and custom groups are not in the BigQuery export schema. Google also warns that a group with a large number of fields "may negatively impact your reports".

Google's own example is a beachwear brand's summer campaign: a group called "Summer Swim Social Media" that keeps Paid Social and adds one channel per regional Facebook page, each defined by the campaign name and an exact source. Each channel then appears as its own row in the Acquisition reports.

Creating a custom group

You need the Editor role or above on the property.

1. In Admin, under Data display, open Channel groups.
2. Click Create new channel group to start from a copy of the default group, or copy one of your existing groups.
3. Give the group a name and, if you like, a description.
4. Edit, add or remove channels. A new channel gets one or more condition groups built from the fields listed above.
5. Click Reorder and drag channels into the order you need, then Apply.
6. Click Save group.

Order is the step to get right. In Google's words, "Traffic is included in the first channel whose definition it matches given the current order of channels in the group." A new channel for, say, partner sites placed below Referral can stay empty, because Referral catches the matching traffic first. Google's AI assistant example makes the same point and tells you to move that channel above Referral.

The primary channel group

The primary channel group is the editable stand-in for the default. It starts with the same definition as the default channel group. At the top of the Channel groups admin page, the pencil icon lets you pick any one of your custom groups as the new definition.

Unlike a custom group, a new primary definition is not retroactive: "Data will populate using the new criteria from that point forward." Google calls the primary channel group "an active record" of your channel grouping over time. So the switch is worth making once the custom group is tested, and worth noting in your reporting so a change between two months is not mistaken for a change in traffic.

Editing and deleting groups

Google lists what happens when a custom group changes:

• Reports, explorations and segments: the new definition applies to the underlying data at once, which "may lead to inconsistencies with other reports".
• Audiences: eligibility changes from then on; the change is not applied retroactively.
• Expanded data sets (Analytics 360): keep the earlier definition and fall out of sync, and Google says they "shouldn't be utilized".
• Deleting a group: irreversible. Reports, audiences and expanded data sets that used it show the dimension as unavailable until someone updates them.

Before deleting a group, check which audiences and saved explorations use it.

A checklist

Our suggestions, based on the rules above:

• Look at the Unassigned row in Traffic acquisition each month and trace it back to the links that caused it.
• Fix tagging first. Use a custom group for traffic you cannot re-tag, or for splits the default group doesn't make, such as one channel per partner or region.
• Start every custom group from a copy of the default, and put new channels above the broad ones (Referral, Organic Search) they would otherwise fall into.
• Remember the limit of two custom groups on a standard property; plan them before creating test groups.
• Switch the primary channel group only after the custom group has been checked against a few months of data, and write down the date.
• Add payment and booking domains to the unwanted referrals list so they don't take credit for orders.

Channel groups then feed the monthly numbers in our monthly website report guide.

Frequently asked questions

Can I edit the default channel group in GA4?

No. Google keeps one default channel group for every property. You can create custom channel groups and set one of them as the property's primary channel group, which acts as your editable default.

Why is my traffic Unassigned in GA4?

Unassigned is the value GA4 uses when no channel rule matches the event data. The usual cause is a UTM medium that no default rule recognises. Fix the tags, or add a channel for that medium in a custom channel group.

How many custom channel groups can a GA4 property have?

Two on a standard property and five on an Analytics 360 property, in addition to the default group. Each group can hold 50 channels.

Do custom channel groups work on past data?

Yes. Google says custom channel groups can be applied to reports retroactively. A new primary channel group definition is different: it only applies from the moment you set it.

Why does a channel get traffic I expected in another channel?

GA4 puts traffic in the first channel whose rules it matches, in the group's current order. Move the more specific channel above the broader one.

Where does ChatGPT traffic show up in GA4?

In the default AI Assistant channel, which Google added in May 2026. The medium is set to "ai-assistant" when the referrer matches a recognised AI assistant. Google's AI Overviews and AI Mode remain in Organic Search.

Clean channel data starts with how a site and its campaigns are set up: one GA4 tag on every page, tagged campaign links and key events on real enquiries. That is part of our website development work. See all our services, or email [email protected].