Google's Gemini assistant stopped attaching the tracking tag utm_source=gemini to the source links cited in its answers at the end of September 2026, roughly three weeks after it began adding the tag without documentation, according to server-log data published by search consultant Natzir Turrado and reported by Search Engine Roundtable on October 30. Desktop visits from Gemini can still be identified through the referrer that browsers pass along. Visits that reach websites with no referrer, which analytics tools file as direct traffic, have lost a label that for a few weeks made some of them attributable to Gemini.

In Short

For about three weeks in September 2026, Google's Gemini chatbot added a small label, utm_source=gemini, to the web addresses it cited, so websites could tell which visitors had come from Gemini. Around September 29 the label disappeared, and Google has not said why or whether it will return. Visits from Gemini in a desktop browser can still be traced, but many clicks from the Gemini phone apps arrive with no sign of where they came from, so analytics tools count them as if people had typed the address themselves.

Three weeks of tags

Barry Schwartz reported the change on Search Engine Roundtable on October 30, 2026. "Google seems to have stopped appending UTM parameters on Gemini links, the cited URLs in Gemini's AI responses," he wrote. "Google started adding UTM parameters to links in Gemini in early September, but then, around September 28th, Google stopped." The parameter, according to the report, "was utm_source=gemini but I do not see them on any Gemini links anymore."

UTM parameters are key-value pairs added to the end of a URL after a question mark. Analytics tools such as Google Analytics 4 read them when the visitor lands and use the utm_source value to credit the visit to a named source, whatever else the browser does or does not report about the click. A link that carries utm_source=gemini identifies itself, even when nothing else does.

The evidence for the change comes from server logs. Turrado, who describes his work on X as helping brands grow their visibility in Google and AI search, published a chart under the headline "Gemini's UTM tags grew for three weeks, then vanished overnight." It plots "Daily visits tagged utm_source=gemini," taken from "server logs" with "bots removed." The series begins with one to three tagged visits a day from around September 9, climbs into double figures in the third week of the month and peaks at 83 on the bar aligned with September 28. The next bar shows 3. After that, the chart records scattered days with one or two tagged visits through late October, which it does not explain.

Two annotations frame the bars. A vertical line marks "Oct 1: SEO press reports the tags." A note underneath reads: "Visits with a gemini.google.com referer stayed flat the whole time."

Turrado's longer write-up, The State of AI Traffic Measurability (2026), first published on his site on May 17, 2026 and updated on October 27, dates the disappearance to September 29. According to that analysis, Gemini began adding the undocumented tag to some of its links in September 2026, and by the week of September 21 about two out of three visits arriving with a Gemini referrer in his logs carried it. Then the tag vanished overnight, and the post says it has not reappeared. The two dates do not conflict. The chart's peak falls on September 28, and the collapse to 3 comes the following day.

How the thread unfolded on X

Turrado raised the question publicly on October 27. "¿Remember the Gemini UTM parameter? It's gone... Does anyone else see the same thing?" he wrote. Later that day he followed up: "Not just me. @Xyborg sees the same drop around Sep 28 in Gemini's answers! The cited URLs stopped carrying utm_source." The @Xyborg account belongs to Martín Aberastegue Catena. Turrado added that he had included the finding in "my post on the state of AI traffic measurement," and he copied Schwartz.

The exchange that followed was brief. Schwartz asked: "and still gone?" Turrado replied: "yup!" On October 28 Schwartz put a second question: "but it does pass referrer data? gemini?" Aberastegue Catena answered: "yes, it does."

Turrado then drew the line that matters most for measurement. "On web, yes. From the iOS app, no. It opens links in its own WebView and sends no referrer, so in GA4 it lands in Direct. The only trace is the GeminiiOS user agent in server logs, the one I found and @rustybrick covered." He posted a new test comparing the iOS app with the web app alongside it. Schwartz, whose X handle is @rustybrick, carried that distinction into his report: "Google does still pass the referrer data from the desktop version of Gemini and he said visits with a gemini.google.com referer stayed flat the whole time. But Google seems to have removed the UTM parameters it started adding in September."

Reported after it was gone

The tag's short public record has an odd sequence. Search Engine Journal published "Google Gemini Adds UTM Parameters For Referral Attribution" on October 1, 2026, under the byline of Roger Montti. That article said the change had been spotted in a Reddit discussion, that Google's implementation was undocumented and that it was not known under what circumstances the tags appeared. By Turrado's logs, the tag had stopped appearing two days before the article was published.

Google's John Mueller joined the Reddit discussion. According to Search Engine Journal, he wrote that he could see the tags too, asked whether Gemini did not already pass a referrer, offered to forward reproducible information about referrer problems to the team responsible, and said it would be good to keep referrers in addition to the UTM tagging. Schwartz's report recalls the exchange: "John Mueller from Google even commented on Reddit that he saw the UTM parameters on Gemini links a month or so ago."

Google published no documentation when the tag appeared and none when it went. Search Engine Roundtable's report contains no statement from the company, and it describes the change only as something Google "seems" to have done.

Referrers, apps and the Direct bucket

Why does a tag matter when a referrer exists? On desktop, a click on a cited link carries a referrer naming gemini.google.com, and Turrado's chart indicates that this signal held steady while the tag came and went. GA4 classifies such visits as referrals. Since May 13, 2026, Google Analytics has also included an AI Assistant channel in its Default Channel Group, which collects sessions whose referrer matches a recognised AI assistant. Google's Help Center did not list which assistants were recognised when the channel launched.

The apps are a different matter. In Turrado's description, the Gemini iOS app opens links in a WebView, a browser component embedded inside the app, and sends no referrer. With neither a referrer nor a tag, GA4 places the session in Direct, the bucket for visits with no identifiable source. Server logs can still pick out the visits by their user agent. PPC Land reported in October 2025 that Turrado had found the GeminiiOS user agent while analysing access logs, confirming on October 27, 2025 that the traffic came from the WebView inside the Gemini iOS app. The string combines a GoogleWv/1.0 (WKWebView) token with a GeminiiOS version number. Raw server logs, however, are not part of a standard GA4 report.

On Android, the trail is thinner still. Turrado's analysis says Gemini traffic from Android landed in Direct in nearly every case, and that the Android app has no documented user agent of its own, falling under Google's generic agent or into Direct.

That gap is where the tag earned its keep. While it lasted, according to Turrado, the utm_source=gemini parameter also appeared on visits that arrived with no referrer at all. In his data, for every Gemini visit with a referrer, between 0.16 and 0.65 arrived without one, not counting the iOS app. Put differently, the tag surfaced between 16 and 65 extra Gemini visits for every 100 that the referrer alone identified. Turrado treats that range as a floor, because the test did not reach every user. Adding the iOS app traffic to what surfaced during the tagging period, he puts Gemini's minimum share of Direct at between 0.05% and 0.23% in a normal week.

Those figures carry limits that the post itself leaves open. It does not say how many sites they come from, gives no dates for the "normal week," and does not define the test. The counts in the chart are small, never above 83 visits a day. Aberastegue Catena's observation of the same drop is a second, independent data point, but no figures from his sites appeared in the thread.

The ChatGPT episode in October

OpenAI's assistant went through something similar barely a week later, with a different ending. ChatGPT had extended UTM tagging to links in its "More" section on June 13, 2025, after previously tagging only citation links; before that, "More" links were counted as direct traffic. On October 14, 2026, Search Engine Roundtable reported that utm_source=chatgpt.com had disappeared from ChatGPT links with the release of GPT-6 about a week earlier. Cedric Huesler of Adobe, who raised it on LinkedIn, compared about 500 pages between October 9 and 13 with the previous week and found roughly 31,000 fewer ChatGPT visits and 26,000 more direct visits a day, according to the report. An update on October 15 said the tags had returned, and Huesler called the episode a bug.

Turrado's post records the ChatGPT gap as running from October 7 to 16. During that time, according to his analysis, the ChatGPT channel lost between 68% and 74% of its visits in server logs, while GA4 showed drops of 20%, 46% and 60%, depending on the site. The missing visits could not be found inside Direct, he writes, because Direct's day-to-day swings were as large as, or larger than, what ChatGPT had lost.

That observation explains why a disappearing tag can go unnoticed from inside an analytics account. Untagged visits sink into a bucket whose ordinary variance is larger than they are, and nothing in the dashboard flags the change. ChatGPT's tag came back after little more than a week. Gemini's had been missing for a month when Schwartz checked on October 30.

Why the change matters

Gemini is no longer a marginal source of visits. Alphabet said on October 28, 2026 that the Gemini app had passed one billion monthly active users, up from 650 million a year earlier. Earlier in the year, Similarweb data put Gemini at 22% of global AI website traffic in mid-January, up from 19.5% a month before, while ChatGPT's share slipped to 64.6%. Neither figure measures clicks to outside websites. Both indicate the size of the audience whose outbound visits are now harder to count.

Measuring AI referral traffic has run into the same wall repeatedly: the click leaves the assistant, but the label does not travel with it. In May 2025, Google acknowledged that links in its new AI search experience carried noreferrer attributes that stripped referrer data, so visits from AI Mode were recorded as direct or unknown; Google confirmed on May 23, 2025 that this was unintentional. Three months later, Google Analytics documentation began suggesting a custom "AI Chatbots" channel built on a regular expression that matches gemini among other assistant names. Similarweb research published in June 2026 found that 55.9% of visits influenced by an AI recommendation arrived through search rather than through any AI channel.

Advertising platforms have handled tagging changes differently. Microsoft Advertising emailed advertisers on June 5, 2026 about a change to its UTM auto-tagging, three months before it took effect on September 2, 2026, and set out separate utm_source and utm_medium values for each campaign type. Gemini's tag appeared and disappeared within September, the month Microsoft's change went live, with no notice at either end.

For publishers weighing what AI citations are worth, and for marketers comparing organic AI visibility with paid channels, the result is three kinds of Gemini traffic measured three different ways. Desktop web visits remain identifiable by referrer. Visits from the iOS app show up in server logs through the GeminiiOS user agent but sit in Direct inside GA4. Android visits, by Turrado's account, can mostly not be told apart at all. For three weeks in September, one parameter cut across all three.

What the evidence does not establish

The record leaves several questions open. Google has not said whether the tags were a limited test, a rollout that was reversed, or a fault. Search Engine Journal's October 1 report said it was unknown when the tags were triggered, and Turrado writes that the test did not reach every user, which suggests that not every Gemini user ever received tagged links.

The measurement rests on a small base. Turrado's chart covers logs from the sites he measures, his post does not state how many sites they include, and Aberastegue Catena's confirmation came without numbers. The scattered tagged visits that the chart still shows in October are not explained by either source.

Nor is there any indication of whether the tag will return. Search Engine Roundtable's report of October 30, more than four weeks after the drop, found no Gemini links still carrying it.

Timeline

Summary

Who: Google, through its Gemini assistant; Natzir Turrado, a search visibility consultant whose server logs documented the change; Martín Aberastegue Catena, who saw the same drop; Barry Schwartz of Search Engine Roundtable, who reported it; and John Mueller of Google, who had commented on the tags on Reddit.

What: Gemini stopped appending the tracking parameter utm_source=gemini to the links cited in its answers, about three weeks after it began adding the tag without documentation. In Turrado's logs, tagged visits peaked at 83 in a day before falling to 3. Desktop visits still carry a gemini.google.com referrer, but visits from the Gemini apps that arrive with no referrer are counted as Direct in GA4.

When: The tag appeared in early September 2026 and disappeared around September 28-29, 2026. Turrado raised it on X on October 27 and 28, 2026, and Search Engine Roundtable reported it on October 30, 2026.

Where: In the source links of Gemini's answers, on the web and in the mobile apps, and in the server logs and analytics accounts of the websites receiving the clicks.

Why: Google has not explained the change. It matters because UTM tags were, for three weeks, the one signal that attributed some referrer-less Gemini visits to Gemini, at a time when the Gemini app has passed one billion monthly users and AI assistants are a growing source of website traffic that standard analytics tools struggle to count.