What counts as AI traffic
AI traffic means visits that arrive through a link in an AI assistant's answer: ChatGPT, Gemini, Microsoft Copilot, Perplexity, Claude, DeepSeek, Grok and a handful of smaller services. Google's own AI features are a separate case. Clicks from AI Overviews and AI Mode count as organic search, so they never show up as AI traffic in GA4.
The distinction matters because the two are measured in completely different ways. GA4 recognises AI assistants by their referrer or a UTM parameter, while Google's AI features are only visible indirectly through Search Console. How to become visible in both in the first place is covered on our Generative Engine Optimization page.
How much AI traffic there is
Measured against total website traffic, the share is still small. Statcounter put it at around 0.25 percent of all referrals in August 2026, SE Ranking at 0.32 percent of all traffic, up from 0.24 percent a year earlier. Within AI referrals, ChatGPT dominates with anywhere from 63 to 92 percent depending on the method; Statcounter's September 2026 figure is about 80 percent. Gemini is growing fastest, while Perplexity and Copilot are losing share.
For some industries the picture looks very different. Software, consulting and complex products often see several times that share, and those visitors arrive with a specific question in mind. The channel is small but growing, and it is harder to measure than any other. That is exactly why it pays to set it up properly before it matters.
GA4's new "AI Assistant" channel
Since 13 May 2026 GA4 has had a default channel for AI traffic, rolled out to most properties by early June. When GA4 recognises an AI assistant from the referrer, it sets the medium to ai-assistant and the campaign to (ai-assistant). The "AI Assistant" channel applies whenever the medium is ai-assistant. No setup required.
Three limitations are worth knowing:
- The list is incomplete: Google gives ChatGPT, Gemini, DeepSeek, Copilot and Grok as examples but has not published a full list. Several analyses report that visits from Perplexity and Claude still land in "Referral".
- Not retroactive: sessions from before the change stay in "Referral", so the default channel cannot be compared with 2025.
- It depends on the referrer: without one the channel does not apply, even when a UTM parameter gives the sender away. More on that below.
What GA4 still misses
A large share of AI traffic arrives without any sender information. The ChatGPT app and other assistant apps often open links without a referrer, and many people copy a link from the chat into a new browser tab. Both end up as "Direct" in GA4.
ChatGPT partly compensates by appending utm_source=chatgpt.com to many links, most reliably to source citations. If the referrer is missing, the session has a source but no medium, and GA4 typically files it under "Unassigned" rather than "AI Assistant".
October showed how fragile this is. From 8 to 15 October 2026, right after GPT-6 launched, both the UTM parameter and the referrer went missing, and ChatGPT clicks landed almost entirely in "Direct" that week. According to Adobe, OpenAI confirmed it as a bug, and the UTM parameter has been back since 15 October. The referrer, however, is still missing on most clicks. GA4 does not correct sessions that have already been recorded.
A custom channel group in five steps
The most reliable fix is a custom channel group that recognises AI assistants by source, regardless of medium or referrer. Google describes this exact approach as an example in its own help pages. One advantage over the default channel: custom channel groups apply retroactively, including to 2025 data.
- In GA4, go to Admin → Data display → Channel groups and copy the default channel group.
- In the copy, create a channel called "AI assistants".
- Condition: Source matches regex, using the expression below.
- Move the channel to the top, at least above "Referral" and "Unassigned". GA4 assigns each session to the first channel it matches.
- Save, then select the new channel group as the primary dimension in your acquisition reports.
^(.*\.)?(chatgpt\.com|openai\.com|perplexity\.ai|claude\.ai|gemini\.google\.com|copilot\.microsoft\.com|deepseek\.com|grok\.com|meta\.ai|mistral\.ai|you\.com|poe\.com)$|^(chatgpt|perplexity|claude|gemini|copilot)$The expression covers the main assistants' domains including subdomains such as chat.openai.com or chat.mistral.ai, plus sources consisting of just the name. Standard properties get two custom channel groups with up to 50 channels each. To add a new service, just extend the expression. You will find the relevant sources in the "Traffic acquisition" report under the "Session source" dimension.
Search Console and Bing: visibility without clicks
GA4 cannot see Google's own AI features, which is where Search Console comes in. Generative AI reports appeared there in June 2026 and have been available to all properties since late August. They show how often your pages appear in AI Overviews and AI Mode, but no clicks and no queries. More in our fall SEO update.
Bing Webmaster Tools offers something similar for Microsoft Copilot. Since February 2026 its "AI Performance" report has counted how often your pages are cited in Copilot and in Bing's AI answers, along with the underlying queries. Clicks are missing here too. Both reports show visibility; GA4 shows the part of it that turns into a visit.
Narrowing down invisible AI traffic
No tool can cleanly attribute the share that arrives as "Direct". You can still narrow it down:
- Watch deep pages: direct visits to individual articles or product pages that nobody types in by hand are often links copied from a chat. If they rise on pages that also get visits from AI assistants, that is a strong signal.
- Check new users: genuine direct traffic mostly comes from returning visitors. Lots of new users in "Direct" on a specialist page point to AI assistants.
- Annotate breaks: mark 8 to 15 October 2026 in GA4 so the dip is not read as a decline.
- Just ask: a required "How did you hear about us?" field with a "ChatGPT or another AI assistant" option in your contact or checkout form often gives B2B companies the most honest number.
- Tag your own links: wherever you place links yourself, for example in profiles or directories that AI assistants like to cite, UTM parameters make things clear. Our UTM generator also shows which GA4 channel the link will end up in.
Our recommendation
Treat the AI channel figure as a floor. What shows up there definitely came from an AI assistant, but part of the real volume sits in "Direct" and "Unassigned". In our reporting we therefore show three figures side by side: the custom "AI assistants" channel for the trend over time, the AI reports from Search Console and Bing for visibility, and direct visits to specialist pages as a hint at the rest. The trend matters more than the exact number, and a clean channel group lets you read it reliably, even retroactively.
Whether your site is easy for AI assistants to read in the first place is something our free GEO checker tells you. If you want help with GA4 and channel groups, our approach is described on the Google Analytics 4 page.
FAQ
How do I see ChatGPT traffic in GA4?
Through the AI Assistant channel when a referrer is passed. Since it is usually missing, many visits land in Unassigned. A custom channel group by session source is more reliable.
Do AI Overviews count as AI traffic?
No, GA4 counts them as organic search. Search Console shows their visibility, as impressions only.
Does GA4 recognise Perplexity and Claude?
Not reliably. The custom channel group with the expression above closes the gap.
Why was ChatGPT traffic missing in October?
From 8 to 15 October 2026 the UTM parameter and referrer were missing. A bug according to Adobe, fixed since 15 October.
Do custom channel groups apply retroactively?
Yes, unlike the default AI Assistant channel.