ChatGPT UTM Bug Sent Referral Traffic to Direct During the GPT-6 Rollout
A temporary change in how ChatGPT handled outbound links distorted a key marketing metric during the GPT-6 rollout in October 2026. UTM parameters identifying ChatGPT as the source disappeared from some links, while browser settings on some opened links also suppressed referrer information. The result was not necessarily a decline in ChatGPT-driven visits. Instead, analytics platforms such as…
During the GPT-6 rollout in October 2026, a bug in how ChatGPT handled outbound links caused referral traffic to appear as Direct or Unassigned traffic in analytics platforms like Google Analytics 4. UTM parameters, which identify ChatGPT as the source, disappeared from some links, while browser settings suppressed referrer information on opened links.
This led to a temporary dip in ChatGPT-attributed traffic, while Direct traffic increased by roughly 26,000 visits per day. The incident demonstrates the importance of monitoring channel attribution during AI-driven browsing, as AI assistants can create measurement dependencies outside a website owner's control. Businesses should document anomalies and review total sessions, conversions, and adjacent channels before making decisions based on short reporting windows.
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