Referrer behaviour changelog
Dated changes in how AI assistants and analytics tools label AI traffic. Every entry has its sources and a status, and says when it is only reported by one party.
Last checked · How we check
- Open: a fix is reported by one person, not confirmed publicly
ChatGPT clicks lose utm_source and referrer in GA4 data
From 9 October 2026, analysts reported fewer ChatGPT sessions and more Direct sessions. A fix is said to have started rolling out on 15 October.
Sources: Search Engine Journal, 15 Oct 2026, Relevant Audience
- Released; the list of recognised assistants is described differently by two sources
GA4 adds an AI Assistant channel
A release note describes the AI Assistant channel in the default channel group, with medium ai-assistant and campaign (ai-assistant). The note names ChatGPT, Gemini and Claude.
Sources: Google Analytics Help: release notes
- Reported by a secondary source
Reports of utm_source=chatgpt.com on more ChatGPT links
Trade press reported from 13 June 2025 that ChatGPT appends utm_source=chatgpt.com to more links, including links under "More".
Sources: PPC Land
How entries are written
An entry appears when at least one source we can link reports a change in the referrer, the utm tag or an analytics tool's classification. We state who reported it, what they measured and what we could not verify. An entry stays open until a primary statement or repeated reports settle it. The methodology explains the labels.
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