TLDR
GPT-6 changed how ChatGPT opens links, dropping the UTM tracking tag and the referrer header that analytics platforms use to identify AI referral traffic. Cedric Huesler of Adobe found ChatGPT-attributed visits fell about 31,000 a day across 500 pages while direct traffic rose 26,000 a day on the same URLs. Marketers should cross-check direct traffic trends against ChatGPT referral data before reporting AI search performance.
KEY TAKEAWAYS
What changed in the data, and when
GPT-6 rolled out to ChatGPT Plus, Pro, Business and Enterprise users on 7 October 2026, and to Free and Go tiers the following day.[1] Within 48 hours, analytics dashboards across the industry started showing numbers that did not add up.
Cedric Huesler of Adobe pulled data from roughly 500 pages where ChatGPT had been driving at least 5 per cent of visits. Comparing the week of 9 to 13 October against the prior week, he found ChatGPT-attributed sessions had dropped by about 31,000 visits a day while direct traffic on those exact same pages had risen by about 26,000 visits a day.[2] Organic search on the same pages fell 7 per cent, matching wider background trends, which ruled it out as a cause.
The gap between those two numbers, roughly 5,000 visits a day, suggests some ChatGPT-driven sessions are not migrating cleanly into the direct channel. Where they are going is not yet clear from the data.
Since octobre 9th I also see a sharp drop in Chat GPT human traffic, and also a drop of Chatgpt-user robot traffic. OAi Search bot traffic has increased in the same time (sinc october 7th be precise). Am going to investigate the utm parameter.
2026-10-14 · View on XFrench SEO consultant Sébastien Billard reported the same pattern independently on 14 October, noting a sharp drop in ChatGPT human traffic and ChatGPT-User bot traffic since 9 October, while OAI-SearchBot crawling had increased since 7 October.[2]
How GA4 ends up filing ChatGPT clicks as direct
Huesler said GPT-6 opens links with window.open(url, '_blank', 'noopener,noreferrer'), which drops the ?utm_source=chatgpt.com tag and kills the referrer header, leaving Google Analytics 4 (GA4) nothing to attach the session to, so it files the visit under Direct.[2]
When a browser opens a link with the noreferrer attribute, it deliberately withholds the page the visitor came from. Without that referrer header, GA4 cannot identify the source. OpenAI's own help pages say ChatGPT adds utm_source=chatgpt.com to referral URLs so publishers can track inbound traffic.[3] Huesler found links opened by GPT-6 no longer carry it.
GA4 had already given this category of traffic its own home. On 13 May 2026, GA4 introduced a dedicated AI Assistant channel, grouping chatbot referrers including ChatGPT under the medium "ai-assistant".[4]
Google's Gemini had already added UTM tags to its outbound links before ChatGPT did, giving practitioners a clean comparison between the two AI referral sources. OpenAI introduced UTM tracking to ChatGPT links in June 2026, only to remove it, apparently, with the GPT-6 rollout four months later.[2] As of 14 October 2026, OpenAI had not confirmed whether the change was intentional.[5]
What to check in your analytics now
Anyone reporting AI search performance to clients or leadership should pull their direct traffic trend starting from 7 October and compare it against ChatGPT referral data for the same pages. A simultaneous drop in the AI Assistant channel and a rise in direct on the same URLs is the fingerprint of this issue, not a sign that ChatGPT stopped sending readers.
Until OpenAI clarifies its position, any dashboard showing ChatGPT referral data from 7 October onward may be undercounting AI-driven visits, with the missing sessions absorbed into direct.
SOURCES & CITATIONS
FREQUENTLY ASKED QUESTIONS
Why did ChatGPT referral traffic drop after GPT-6 launched?
Has actual traffic from ChatGPT fallen, or is this just a measurement problem?
What should marketers check in their analytics right now?
James Dore is founder and editor of Prompt the Market and Strategy Director at Bushnote, a Sydney strategy, SEO and AI search agency. He has a background in strategy, media and financial services, and led consumer product marketing at MONEYME. He writes on AI search, answer engines, technology policy and media economics.
