GPT-6: a bug filed ChatGPT visits as direct traffic in GA4
Partner · Strategy, advertising and measurement
From the launch of GPT-6 on October 7 and 8, 2026, until October 15, links clicked in ChatGPT reached websites without the utm_source parameter and without a referrer. Google Analytics 4 therefore filed these visits under direct traffic. It was a bug: OpenAI confirmed it to Cedric Huesler (Adobe) on October 14, with no public announcement, and the fix brought the parameter back on October 15. If traffic from ChatGPT dropped in your reports during that week while direct traffic went up, you are most likely looking at a measurement problem, not a loss of visibility.
What happened
Since June 2025, ChatGPT added a utm_source=chatgpt.com parameter to the links in its answers: first to cited sources, then to the links in the "More" section. GA4 could therefore attribute these visits to ChatGPT even when the referrer (the page the click came from) was not passed along.
Cedric Huesler, of Adobe, found the cause on October 13. GPT-6 was opening links with a browser function (window.open with the "noopener" and "noreferrer" options) that passed neither the parameter nor the referrer. He compared October 9 to 13 with the previous week on about 500 pages where ChatGPT brought at least 5% of visits.
Before the bug
The link carries the utm_source=chatgpt.com parameter. GA4 attributes the visit to ChatGPT, even without a referrer.
During the bug, October 8 to 15
The link opened without a parameter or a referrer. GA4 had nothing to read and filed the visit under direct traffic.
Direct traffic rose on two out of three pages that lost ChatGPT traffic (261 pages out of 387). The week before, it was one page out of two. On mobile, the share of direct visitors who saw the consent banner (new visitors, in other words) rose from 36% to 44% on these pages, against 55% among visitors coming from ChatGPT: the new "direct" visitors look like ChatGPT visitors. Huesler states the limits of his measurement himself: four days of data, a sample, and pages where ChatGPT already carried a lot of weight.
Two details come from the infographic Adobe published with the analysis. Before GPT-6, the referrer already reached only about 12% of clicks: the parameter did almost all the attribution work. And Adobe places the GPT-6 rollout between October 8 and 10, where other observers date it to October 7 and 8. Across thousands of sites tracked by Adobe, visits attributed to ChatGPT lost two thirds in a week.
Barry Schwartz (Search Engine Roundtable) relayed the analysis on the morning of October 14. SEO specialist Sébastien Billard observed, on his side, a sharp drop in human traffic from ChatGPT since October 9. OpenAI made no announcement. Schwartz himself wrote that he did not know whether the change was intended.
The October 15 fix
Times are Montreal time.
- October 14, noon: Cedric Huesler writes to OpenAI. Two hours later, he is told it is a known bug and that a fix is planned for that week.
- October 15, around 5 a.m.: the fix starts rolling out in stages. By noon, clicks carrying the utm_source=chatgpt.com parameter are back to roughly 95 to 100% of their level at the same hour the week before, across the thousands of sites Adobe tracks. Huesler updates his post the same day: "it was a bug."
- In the following days: SEO consultant Glenn Gabe tells Huesler he does not yet see the change on his ChatGPT accounts, free or paid. The fix may not have reached every user on the same day.
- October 26: a link to our own site, given by ChatGPT, carries the utm_source=chatgpt.com parameter again.
Two caveats remain. The confirmation is secondhand: it comes from Huesler. OpenAI has published nothing, neither an announcement nor a line in its release notes. The referrer is also still missing on most clicks from ChatGPT: the parameter remains the only reliable signal for attributing these visits, and OpenAI can remove it overnight.
Who was affected
Every company that tracks visits from AI assistants in GA4 or in another analytics tool: custom channel groups, segments, Looker Studio dashboards. Online stores and B2B companies that received a visible share of their visits from ChatGPT noticed it first.
Conversions followed the same path. A sale or a quote request that started with a click in ChatGPT during that week is credited to direct traffic in your reports. GA4 will not reclassify these visits after the fact.
The bug came from how ChatGPT works and did not depend on the country: it affected visits from users in Quebec, whether the conversation is in French or in English. In Quebec, Law 25 already requires consent before analytics cookies are set. Part of the visits from ChatGPT was therefore already missing from your reports. During the bug, the visible share shrank further.
Gemini: a parameter that came and went
The same mechanism played out at Google, in the opposite direction. In early September 2026, Gemini started adding a utm_source=gemini parameter to the links it cites in its answers, without announcing it. Consultant Natzir Turrado found it in his server logs from about September 9; in the week of September 21, two out of three visits from Gemini carried the parameter. On September 28, his logs count 83 tagged visits in the day; the next day, 3. The parameter had not returned as of October 30, when Barry Schwartz relayed the observation. Google has explained nothing: not a test, not a rollback, not a fault.
The effect in GA4 is more limited than for ChatGPT. On desktop, Gemini passes the gemini.google.com referrer, which stayed flat throughout, and those visits are classified as referrals. In the iOS app, links open in an in-app window that sends no referrer: those visits land in direct traffic, and only server logs can identify them. On Android, Turrado judges that they cannot be separated reliably. The annotations and checks recommended below therefore apply to Gemini too.
What we recommend
- Add an annotation from October 7 to 15, 2026 in your reports and dashboards (GPT-6 reached paid plans on October 7 and free plans on October 8). It will keep the drop from being read as a loss of visibility three months from now.
- Compare direct traffic to your deep pages (articles, product pages, service pages) during that week and the week before. Few people type these addresses from memory: a rise in direct traffic on these pages often points to visits from an AI assistant.
- Track your presence in ChatGPT with a citation-tracking tool rather than with referral traffic alone. We compare these tools in our analysis of AI visibility tools.
- Add the question "How did you hear about our company?" to your forms, with ChatGPT among the choices. We did it on our own forms.
- Keep your current settings. The parameter is back and your reports picked it up again without any change: there is no need to rebuild your attribution models over one week of data.
Reading what ChatGPT says about you when traffic no longer shows it is part of what our AI visibility and GEO service covers.
A drop in ChatGPT traffic in your reports from October 8 to 15, 2026 does not mean a drop in visibility: it was a measurement bug, fixed on October 15. A drop that continues after that date has another explanation.
What these visits are worth once measured is covered in does AI traffic convert better. The limits of consent-based measurement are explained in consent and measurement: the limits of Google Consent Mode. To understand where ChatGPT gets its links, see what search engine does ChatGPT use.
- Search Engine Roundtable, OpenAI Drops UTM Parameters From ChatGPT Results (GPT-6), October 14, 2026. Source for the relay of the analysis, the absence of an announcement from OpenAI and the link with the GPT-6 release. The October 15 update reports that it was a bug.
- Cedric Huesler (Adobe), LinkedIn post, October 13, 2026, updated October 15. Source for the technical cause, the October 9 to 13 figures, the limits of the measurement and the bug confirmation.
- Relevant Audience, ChatGPT UTM tag loss was a bug, says Adobe's Huesler; fix rolling out, October 16, 2026. Source for the times of the confirmation and the fix, the return to 95 to 100% of tagged clicks, the referrer still missing, the absence of any mention in OpenAI's release notes and Glenn Gabe's observation.
- Dalin de Graff, ChatGPT UTM Tags Disappeared With GPT-6, October 14, 2026. Source for the GPT-6 rollout dates (October 7 for paid plans, October 8 for free plans).
- Sébastien Billard, post on X, October 14, 2026. Drop in human traffic from ChatGPT since October 9.
- PPC Land, ChatGPT adds UTM parameters to more links for better analytics tracking, June 16, 2025. Source for the parameter being added to the links in the "More" section.
- Search Engine Roundtable, OpenAI's ChatGPT Updates To Improve Tracking In Analytics, June 16, 2025. Source for the start of link tagging in June 2025.
- Adobe Brand Visibility, infographic "Where did ChatGPT's visitors go?" published with Cedric Huesler's analysis and relayed by Search Engine Roundtable, October 14, 2026. Source for the indexed curve, the 261 pages out of 387, the 12% share and the October 8 to 10 rollout window.
- PPC Land, Google Gemini drops UTM tags from cited links after three weeks, Luís Rijo, November 1, 2026, based on the observation relayed by Barry Schwartz (Search Engine Roundtable) on October 30. Source of the utm_source=gemini parameter, the September dates, the figures from Natzir Turrado's logs, the gemini.google.com referrer on desktop, the iOS and Android app cases and Google's lack of explanation.
Gabriel almost always takes your first call and carries out your audit. He builds the strategy starting from your growth goal: where to put your budget, which market to test and how to connect each lead to a real sale in your CRM. He mainly leads engagements for three goals: Optimize the profitability of your digital campaigns, Develop a new market, and Generate demand and growth. With Geneviève, he also works on organic search (SEO), AI visibility (GEO) and conversion rate optimization (CRO). The sales a Google Ads or Meta Ads campaign brings in depend on the page that receives the click. He writes mainly about marketing strategy, paid advertising and measurement.
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