- Google Analytics added an AI Assistant channel to the default channel group on May 13, 2026. [1]
- It applies when the referrer matches Google’s list of AI assistants. The medium becomes ai-assistant and the campaign (ai-assistant). [1][2]
- The channel excludes AI Overviews and AI Mode. Google’s definition of Organic Search includes them. [2]
- Search Console counts both inside the Web search type and documents no separate filter. [3]
- The ?st_source=ai_overview parameter seen on AI Overview links on October 2 came from a browser extension, not Google. [4]
- Gemini has started adding UTM parameters to outbound links. Google has not documented them. [5]
- OpenAI says ChatGPT adds utm_source=chatgpt.com to referral URLs. [6]
- In August we wrote that no default AI channel existed. That was wrong, and the original article now carries a correction.
Start with our own error. On August 14 we published a piece on measuring AI traffic whose headline said everyone reports it from a channel grouping that does not exist. Three months earlier, on May 13, 2026, Google Analytics had announced exactly such a grouping. [1] We missed it, the claim was wrong on the day it ran, and the original now says so.
The correction is worth more than an apology, because the channel that exists is not the channel most people assume. It names the traffic that comes from assistants. It does not name the traffic that comes from the AI answers inside Google Search, and that is the larger surface for most sites.
What the channel is
The announcement is short. “Google Analytics now provides a dedicated way to measure and analyze traffic originating from popular AI assistants,” it says, naming ChatGPT, Gemini, and Claude. [1] Three traffic dimensions change: the medium gets a new ai-assistant value, the default channel group gets an AI Assistant channel, and the campaign is labeled (ai-assistant). [1]
The channel definition page gives the rule: the channel applies when the medium exactly matches ai-assistant, and that medium is set “if the referrer matches a list of AI Assistants.” [2] Its examples are ChatGPT, Gemini, Deepseek, Copilot, and Grok. [2]
One word in that rule carries the weight: referrer. The classification happens only when the visit arrives with a referrer Google recognizes. A click that arrives with no referrer has nothing to match.
What Google kept in Organic Search
The same help page that defines the new channel draws its boundary in one sentence: “It excludes Google’s AI Overviews and AI Mode.” [2] A few rows down, the definition of Organic Search picks them up: it covers non-ad links in organic search results, “including Google’s AI Overviews and AI Mode.” [2]
Search Console follows the same logic. Google’s documentation says sites appearing in AI features “are included in the overall search traffic in Search Console” and are reported in the Performance report within the Web search type. [3] It describes no filter that separates them.
ChatGPT, Gemini, Deepseek, Copilot, Grok, and other assistants on Google’s list, when the visit carries a matching referrer. Its own row in the default channel report. [2]
Put plainly, Google’s analytics product will tell you how many visits came from a competitor’s assistant, and from its own Gemini app, and will not tell you how many came from the AI answer at the top of its own results page. We covered what that answer does to click volume in our piece on AI Overviews traffic. The new channel does not change that picture. It sits next to it.
The parameter that was not Google
Briefly, on October 2, it looked as if that gap was closing. Tom Pool posted that he had started seeing a ?st_source=ai_overview parameter on links inside AI Overviews and asked whether it was “the start of actual proper attribution reporting.” Search Engine Roundtable ran it as a Google test. [4]
It was not. The story now carries an update quoting Pool: “Turns out it was a Chrome Browser Extension modifying the URLs to include these parameters.” [4]
The lesson is practical. A parameter you see in your own browser is evidence of what your browser did. Before you build a segment on a query parameter, look for it in your landing page report, across many users, over several days. One screenshot is not a tracking spec.
What Gemini’s tags change
A day earlier, Search Engine Journal reported that Gemini had begun adding UTM parameters to outbound links, after a Reddit user noticed them. Google’s John Mueller replied in the thread: “Nice. I see it too. Doesn’t Gemini have a referrer too though?” [5] When another user said the referrer often does not survive, Mueller answered that he would forward reproducible examples to the team, adding: “It would be great to have these retained (in addition to the UTM-tagging).” [5]
That exchange says two things. A tag on the URL survives where a referrer may not, which is what makes it useful for attribution. OpenAI documents its own: “ChatGPT automatically includes the UTM parameter utm_source=chatgpt.com in referral URLs.” [6] And Google has not documented Gemini’s. Search Engine Journal notes that it is unknown under what circumstances the tags are triggered. [5] So do not hard-code a Gemini parameter value from a screenshot either.
| A visit from | Lands in | Why |
|---|---|---|
| ChatGPT, Gemini, Copilot, with a matching referrer | AI Assistant | The default rule matches the referrer [2] |
| An assistant, with the referrer missing | Not AI Assistant by the default rule | The rule has no referrer to match [2] |
| An AI Overview | Organic Search | Included by Google’s definition [2] |
| AI Mode | Organic Search | Included by Google’s definition [2] |
What to do in your property
Find the row
Open Traffic acquisition with Session default channel group and look for AI Assistant. If it is there, the default rule is already working on your data.
Look for the leak
Switch to Session source / medium and filter the source with the pattern below. Any row whose medium is not ai-assistant is a visit the default channel missed.
Referral, Direct, UnassignedPatch only what leaks
If those rows are material, add one custom channel rule for those sources. If they are not, retire the hand-built AI channel group and use the default, so your numbers match everyone else’s.
chatgpt|openai|gemini|copilot|perplexity|claude|deepseek|grok
The pattern is a starting point, not Google’s list. Add the assistants your audience uses and remove the ones that never appear.
What we said in August about reporting still holds, and holds more firmly: give absolute numbers, name the sources you count, and say what is not counted. The uncounted part now has an official description. It is the part Google files under search.
Sources
- Google Analytics Help · What’s new in Google Analytics: New AI Assistant traffic measurementPrimary. Entry dated May 13, 2026.
- Google Analytics Help · Default channel groupPrimary. Channel descriptions and rule definitions.
- Google Search Central · AI features and your websitePrimary.
- Search Engine Roundtable · Google Tests URL Tracking Parameters To AI Overviews & AI ModeTrade press, October 2, 2026, with an update stating the parameter came from a browser extension.
- Search Engine Journal · Google Gemini Adds UTM Parameters For Referral AttributionTrade press, October 1, 2026. Quotes a Reddit thread; Google has not documented the behavior.
- OpenAI Help Center · Publishers and Developers FAQPrimary.
Frequently asked questions
Does GA4 have an AI channel by default?
Yes. Google Analytics announced AI Assistant traffic measurement on May 13, 2026. Visits whose referrer matches a recognized AI assistant get the medium ai-assistant, the campaign name (ai-assistant), and the AI Assistant channel in the default channel group.
Which assistants does the AI Assistant channel include?
Google’s channel definition gives ChatGPT, Gemini, Deepseek, Copilot, and Grok as examples, and its announcement names ChatGPT, Gemini, and Claude. The rule says the channel applies when the referrer matches a list of AI assistants. The two help pages we read do not print the full list.
Are clicks from AI Overviews in the AI Assistant channel?
No. Google’s definition says the channel excludes Google’s AI Overviews and AI Mode, and its definition of Organic Search says that channel includes them. A click from an AI Overview is reported as organic search.
Can Search Console separate AI Overviews or AI Mode clicks?
Not according to Google’s documentation. It says sites appearing in AI features are included in the overall search traffic in Search Console and reported in the Performance report within the Web search type. It describes no separate filter for them.
Was the st_source=ai_overview parameter a Google test?
No. Search Engine Roundtable first reported it on October 2, 2026 as a possible Google test, then updated the story: the person who spotted it said a Chrome browser extension was modifying the URLs to add the parameter.
Does Gemini add UTM parameters to links?
Search Engine Journal reported on October 1, 2026 that Gemini had started adding UTM parameters to outbound links, and Google’s John Mueller replied to the Reddit thread that he saw it too. Search Engine Journal notes that Google has not documented the behavior, so the conditions under which the tags appear are unknown.
Do I still need a custom channel group for AI traffic?
Only for what the default misses. The default rule depends on the referrer, so check your own reports for sessions whose source is an assistant but whose channel is Referral, Direct, or Unassigned. If you find none, the default channel is enough. If you find some, a narrow custom rule for those sources is justified.
Mikołaj Salecki
Writes about media, tech, and AI business for people who actually run digital. Former agency lead. Skeptic of frameworks that read better than they perform.
