A UTM parameter is a tag on the end of a URL that tells your analytics where a visit came from. For a long time ChatGPT added utm_source=chatgpt.com to the links in its answers, so those visits could be told apart from everything else.
What we measured
On 2026-10-21 we asked ChatGPT 25 questions through its API with search on and looked at every link it returned. All 47 of its 47 citations carried utm_source=openai, the API's version of the same tag.
What changed in October 2026
On 14 October 2026 Search Engine Roundtable reported that ChatGPT had stopped adding the tag and stopped passing a referrer. The observation came from Cedric Huesler of Adobe, who compared about 500 pages where ChatGPT drove at least 5% of visits, over 9 to 13 October, against the week before: ChatGPT-attributed visits fell by about 31,000 a day while Direct rose by about 26,000 a day on the same pages. He attributes it to links opening with noopener and noreferrer after the GPT-6 rollout. OpenAI has not confirmed the change, and the sample is four days from one practitioner, so treat it as a dated observation rather than a rule.
What GA4 does with these visits
Google Analytics has no built-in channel for AI assistants. Its custom channel groups help page shows how to add one with a source regex covering ChatGPT, Gemini, Copilot, Claude and Perplexity, and tells you to place it above Referrals. Ann Smarty, writing in Practical Ecommerce on 11 October 2026, notes that GA4 puts a share of ChatGPT traffic in Direct or Unassigned because of the missing referrer, and suggests searching Session source / medium for "gpt" to see what is still attributable.
What to do
Build the AI Assistants channel now, so the visits that still carry a source are counted together. Then watch Direct traffic to pages that only an assistant would send people to: a long-tail answer page with no ranking and no campaign that suddenly gets Direct visits is probably getting them from ChatGPT.
