Gemini referral traffic is now reported to arrive with UTM parameters, which means visits from Google Gemini can show up in GA4 as tagged traffic instead of disappearing into Direct. Search Engine Journal broke the news on October 1, 2026, but as of October 2026 Google has not documented the change or the exact parameter values.
That gap matters for anyone who reports on AI referral traffic. This guide separates what is confirmed from what is reported, explains how GA4 classifies Gemini visits today, and walks through a setup that keeps working whatever values Gemini ends up using. It is part of our analytics, tracking and privacy hub.
What changed with Gemini referral traffic
Gemini has reportedly started adding UTM parameters to the links it sends people to, so a visit from Gemini can carry its own campaign tags instead of relying on the referrer alone. The change was spotted by a Reddit user and reported by Search Engine Journal on October 1, 2026.
According to Search Engine Journal's report by Roger Montti, a user in the r/SEO subreddit wrote that Gemini had started using UTM parameters "very new 24hours or so", comparing it with ChatGPT. Google's John Mueller replied: "Nice. I see it too. Doesn't Gemini have a referrer too though? I thought you could already track them."
A second Redditor answered that the referrer mostly survives on desktop web and gets lost in the Gemini mobile app and in Android assistant invocations, so many Gemini visits land in Direct. That is a community claim without published data behind it, so treat it as a hypothesis to test in your own property, not a fact. Mueller then said he was happy to forward reproducible referrer examples to the team and that it "would be great to have these retained (in addition to the UTM-tagging)."
What Google has and has not confirmed
Google has not officially announced or documented UTM parameters on Gemini links as of October 2, 2026. The only Google voice on record is Mueller's reply that he sees the parameters too, which confirms the observation but is not documentation.
Here is how the evidence breaks down:
- Reported: Gemini adds UTM parameters to outgoing links (Reddit, via Search Engine Journal). Mueller's "I see it too" supports the observation.
- Not published: the exact Gemini UTM parameter names and values, which Gemini surfaces add them (web, Android app, iOS app) and which answers trigger them. Search Engine Journal says the implementation is undocumented and that it is unknown under what circumstances the UTMs are added.
- Not in the release notes: the Gemini release notes had no entry about outbound link tagging when this post was published. The latest entries were about Skills (September 30, 2026) and the Windows desktop app (September 10, 2026).
- Speculation: that tagging only applies to answers that cite web pages. Search Engine Journal suggests this by analogy with ChatGPT, but Google has not said so.
Because the values are not documented, do not hard-code a single utm_source value into reports yet. Look at what actually arrives in your property first.
How GA4 classifies Gemini referral traffic
GA4 puts Gemini visits with a recognized referrer into the AI Assistant default channel, with the medium ai-assistant and the campaign (ai-assistant). Google added that channel on May 13, 2026.
The GA4 release notes for May 13, 2026 describe the new AI Assistant traffic measurement: the medium "ai-assistant" is assigned automatically when the referrer matches a recognized AI assistant, and the campaign is set to "(ai-assistant)". Google names ChatGPT, Gemini and Claude as examples. The default channel group page lists ChatGPT, Gemini, Deepseek, Copilot and Grok, and states that the channel excludes AI Overviews and AI Mode, which count as Organic Search.
UTM parameters change this picture. Google's documentation on traffic-source dimensions says that when no Google Ads click ID applies and any UTM parameter is present, GA4 derives all cross-channel traffic source values from the UTM parameters exclusively, and missing parameters show as "(not set)". Google does not document how this rule interacts with the AI Assistant medium. Our reading, which is an inference and not documented behavior: if Gemini's tags carry a medium other than ai-assistant, or no medium at all, those sessions could end up in Referral or Unassigned instead of AI Assistant.
That is not a new problem. In a July 2026 analysis for Search Engine Journal, Itamar Blauer showed chatgpt.com traffic split across the ai-assistant, referral and (not set) mediums, and therefore across three channels. The fix is the same for Gemini: build your own channel that looks at source as well as medium.
How AI assistants show up in GA4
AI assistants reach GA4 in three ways: through a referrer that GA4 recognizes, through UTM parameters on the link, or with neither, in which case the visit counts as Direct. The table shows what is documented or reported for each source as of October 2026.
| Source | UTM parameters on links | GA4 default channel | Status |
|---|---|---|---|
| Gemini | Reported since about October 1, 2026; values not published | AI Assistant when the referrer is recognized | UTMs reported (SEJ), channel documented by Google |
| ChatGPT | utm_source=chatgpt.com in referral URLs | AI Assistant when the referrer is recognized | Both documented (OpenAI, Google) |
| Copilot, Deepseek, Grok | No documented tagging | AI Assistant when the referrer is recognized | Channel documented by Google |
| Claude | No documented tagging | Named as an example in the May 13, 2026 GA4 release note | Documented by Google |
| Perplexity | No documented tagging | Reported to stay in Referral | Reported (SEJ, July 2026) |
| Google AI Overviews and AI Mode | No tagging | Organic Search | Documented by Google |
The ChatGPT row comes from OpenAI's publishers and developers FAQ, which says ChatGPT automatically includes utm_source=chatgpt.com in referral URLs. Google does not publish the full list of referrers it treats as AI assistants, so check the default channel group page again before you build a client report on it.
How to track Gemini referral traffic in GA4
The most reliable way to track Gemini referral traffic is a custom channel group with one AI channel that matches either the ai-assistant medium or a regex on AI sources, placed above Referral. That catches recognized referrers, UTM tagged visits and sources GA4 does not recognize yet.
Custom channel groups need the Editor role or higher. Standard properties can have two custom groups and GA4 360 properties five, with up to 50 channels per group, according to Google's custom channel groups documentation. They apply to your reports retroactively.
- Open the channel groups. In GA4, go to "Admin", then "Data display", then "Channel groups".
- Copy the default group. Click "Create new channel group" so you start from the default channels, and name it, for example "Channels with AI".
- Add an AI channel. Click "Add new channel", name it "AI assistants", click "Add condition group" and set "Medium" exactly matches
ai-assistant. - Add the source condition. Add a second condition, joined with OR, on "Source" that matches regex
.*(gemini|chatgpt|openai|perplexity|copilot|claude|deepseek|grok).*, then click "Save channel". - Reorder the channels. Click "Reorder", drag "AI assistants" above "Referral" and "Organic Search", and click "Apply". GA4 assigns traffic to the first channel that matches.
- Save and report. Click "Save group", then open "Reports", "Acquisition", "Traffic acquisition" and pick the new group as the primary dimension.
Review the regex every few months. New assistants appear, and Google itself notes in its AI assistants example that you should update the regex when the list of assistants you want to measure changes. If you want to see how often your brand appears in AI answers in the first place, that is a separate question from referral clicks: see the guide to AI search engine optimization for the visibility side, and the overview of AI visibility tools for ways to track it.
How to check Gemini UTM parameters in your own data
To see which Gemini UTM parameters reach your site, build a free form exploration with "Session source / medium", "Session manual source" and "Landing page + query string", filtered on sources that contain "gemini". The query string shows the exact tags Gemini appended.
In "Explore", start a "Free form" exploration and add those dimensions plus "Page referrer". Filter on "Session source / medium" containing gemini, then look at three things:
- Which source and medium Gemini sessions get. If you see a medium other than
ai-assistant, the UTM tags are overriding the referrer classification. - Which tags appear in the landing page query string. That is the closest you will get to the real Gemini UTM parameters until Google documents them.
- Whether the referrer is present. Sessions with tags but no "Page referrer" are the ones that would have counted as Direct before.
If you have access to server logs or a CDN log, search them for requests with gemini in the query string. Logs see the tagged URL even when the GA4 tag does not fire, for example when consent is declined.
Once Google documents the values, or once you see them consistently in your own data, add an exact match condition on "Session manual source" to the AI channel. Until then, the broad source regex is the safer choice.
How Gemini UTM parameters interact with your own UTM conventions
Gemini's tags are set by Google, not by you, so they sit outside your own UTM naming rules and can collide with them. Keep your conventions for the links you control and treat AI tags as an external input.
Three points help here. First, UTM values are case sensitive: the GA4 URL builder documentation notes that utm_source=google is different from utm_source=Google, so a rule written for one spelling misses the other. Second, if your team already tags links in AI tools by hand, for example in a custom GPT or a chatbot integration, use a different utm_campaign so you can tell your own links from Gemini's tags. Third, keep in mind that a UTM tagged session is attributed like any other session. GA4's attribution settings then decide how much credit AI visits get for key events, which our guide to attribution models explains in detail.
Common mistakes with AI referral traffic tracking
- Copying Google's sample regex unchanged. The AI assistants example in Google's custom channel group help starts with the branch
^.*ai, which is not tied to any assistant name and can match unrelated sources that happen to contain or end in "ai". Use a list of named assistants instead and test it on your source list. - Adding UTM parameters to your own canonical URLs. AI assistants link to the URL they find. Tags on that URL are copied into every other link to the page and mislabel all that traffic. Keep canonical URLs clean.
- Trusting the default AI Assistant channel as the full number. Visits without a recognized referrer or with their own UTM tags can land in Referral, Unassigned or Direct. Compare the default channel with your custom one.
- Expecting AI Overviews and AI Mode in the AI channel. Google counts clicks from them as Organic Search. Report them as part of organic, and do not promise stakeholders a separate number GA4 does not provide.
- Hard-coding a Gemini utm_source value. The values are not documented as of October 2026 and could change. Match on a broad pattern until Google publishes them.
- Reading a jump in Gemini traffic as growth. A rise after October 1, 2026 may only mean that visits once counted as Direct now carry tags. Compare Gemini plus Direct over the same period before you draw conclusions.
