In short. An AI referral appears as Unassigned when its recorded traffic data matches no default channel rule.
Definition: An AI referral can appear as Unassigned in Google Analytics 4 (GA4) when its recorded traffic data matches none of the default channel rules.
Key facts
- As of 17 October 2026, Google's default channel definitions include AI Assistant, with the medium
ai-assistant. - Google's traffic-source reference separates the referring location, called the source, from the traffic type, called the medium.
- Google's Traffic acquisition documentation provides Session source / medium for examining the values associated with a session.
- Google's custom channel documentation allows a separate classification based on source and medium conditions.
Which values explain the channel mismatch?
Google's default channel table assigns Unassigned when no channel rule matches. Referral accepts the medium values referral, app, or link. AI Assistant requires ai-assistant; Analytics sets that medium and the campaign (ai-assistant) when the referrer matches its assistant list.
The practical implication is conditional: an assistant-associated source paired with a different medium can fall into Unassigned if the remaining rules also fail.
A UTM parameter is a campaign label added to a destination URL. Google's campaign-processing documentation explains that custom campaign parameter values populate report dimensions. The document referrer can supply attribution when other campaign or traffic-source fields are absent.
How can the recorded combination be checked?
Google's Traffic acquisition report covers both new and returning users. Its documented report path is:
Reports > Acquisition > Traffic acquisition
An inspection uses Session default channel group to identify Unassigned, then Session source / medium to examine the associated combination. The report also exposes Session source and Session medium separately. These session dimensions describe the user's most recent session, including a returning user's visit.
For manually labelled links, Google's campaign URL guide identifies utm_source as the referrer label and utm_medium as the marketing medium. It recommends including source, medium and campaign parameters together. Missing campaign parameters can produce (not set) values. UTM information appears in Page location; the guide says it is omitted from Landing page + query string and Page path + query string.
How can a separate assistant grouping help?
A custom channel group is a property-defined set of traffic categories. Google's custom channel guide supports Source and Medium conditions and includes an assistant example. Its ordering matters: traffic enters the earliest channel whose conditions it satisfies.
The custom group can be selected in acquisition reports and applied to historical reporting. This provides a way to classify recorded assistant sources under a chosen definition. The same guide distinguishes this from changing the primary channel group, whose new criteria populate that dimension going forward.
Related terms
- GA4 traffic acquisition
- UTM parameters
- How do I create an AI assistants channel in GA4?
- Can a GA4 custom channel group classify historical visits?
FAQ
Does Unassigned identify a particular assistant?
Google's channel definitions define it through unmatched rules. You need the recorded source and medium to investigate the origin.
Can a new campaign tag change an existing session's source?
Google's processing documentation associates each session with one campaign or traffic source. If you send new campaign values during that session, they apply to the collected events and event-based attribution; the existing session retains its campaign and source values.
Sources
- Google Analytics Help, "Default channel group", undated
- Google Analytics Help, "About traffic-source dimensions", undated
- Google Analytics Help, "[GA4] Traffic acquisition report", undated
- Google Analytics Help, "Campaigns and traffic sources", undated
- Google Analytics Help, "URL builders: Collect campaign data with custom URLs", undated
- Google Analytics Help, "Custom channel groups", undated
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