GA4's AI Assistant default channel group now separates traffic from ChatGPT, Gemini, Copilot and others out of Referral. The catch: it only counts forward, Perplexity is missing and a large share of AI visits still lands as Direct.
The dirty secret of AI referral data is the missing referrer. A large share of assistant-driven visits arrive with no header at all and get filed under Direct.
Google Analytics now separates AI assistant traffic into its own channel, and if you have not opened the report yet, this is the prompt. The AI Assistant default channel group automatically classifies sessions arriving from recognised AI referrers, no configuration required, showing engagement, events per session, time on site and conversion performance for visitors sent by chatbots. Practical Ecommerce has a walkthrough of what the reports surface.
The channel recognises ChatGPT, Gemini, Copilot, Deepseek and Grok. When GA4 detects one of those referrers it assigns ai-assistant as the medium and groups the session accordingly. Search Engine Journal covered the mechanics when the channel landed in May.
There are three catches worth knowing before you read the numbers as truth.
The channel only counts forward from mid-May 2026. Everything earlier stays buried in Referral, so year-on-year comparisons will lie to you until next May.
Perplexity is missing from the official definition and still lands in Referral. If your category gets recommended by research-heavy assistants, you are undercounting.
Industry estimates put that dark segment at 20 to 40% of AI-originated visits. The channel is a floor, not a ceiling.
Why it matters
AI assistants are becoming a genuine acquisition source, and the businesses that measure a channel early are the ones that learn to win it. Across the Australian businesses we score, data and tracking is consistently the weakest dimension. A free, automatic report closes part of that gap for zero effort.
Early evidence also suggests AI-referred visitors behave differently. They arrive pre-qualified by a conversation, often deeper in the journey. Knowing whether they convert above or below your site average changes how much you should care about assistant visibility.
The estimated share of AI assistant visits that arrive without a referrer header and land in Direct, meaning the new GA4 channel undercounts the real volume.
What to do about it
Open the report this week. Reports, Acquisition, Traffic acquisition, then find AI Assistant in the default channel group. Note the baseline volume, engagement rate and conversions.
Build a custom channel group for the gaps. Add Perplexity and any other assistant referrers you see in Referral so your definition is more complete than the default.
Compare conversion quality, not just volume. If AI-referred sessions convert at twice your site average, assistant visibility deserves budget and content attention now, not when the volume is large.
Annotate the May start date. Anyone reading your dashboards needs to know the channel has no history, or someone will report a fake growth story.
The measurement layer for AI search just switched on, and the advantage goes to whoever reads it first.