Tracking AI referral traffic in GA4
Create a custom channel group in GA4 with an “AI assistants” channel whose condition is session source matching a regex of AI hostnames, and place it above Referral. This separates visits from ChatGPT, Perplexity, Copilot, Gemini and Claude. It cannot isolate AI Overviews clicks, which arrive as Google organic, and it misses AI visits that carry no referrer.
Steps
- Admin > Data display > Channel groups > Create new channel group (copy the default group).[1]
- Add a channel named “AI assistants”. Condition: Session source > matches regex, using the pattern below.
- Reorder so it sits above Referral; GA4 assigns the first matching channel.[1]
- Save, then use it in Acquisition > Traffic acquisition. Custom channel groups also apply to historical data.
Regex
^(chatgpt\.com|chat\.openai\.com|(www\.)?perplexity\.ai|copilot\.microsoft\.com|gemini\.google\.com|claude\.ai|chat\.deepseek\.com|chat\.mistral\.ai|(www\.)?meta\.ai)$Google’s help page includes its own “AI assistants” example,[1] but a loose pattern that matches “ai” anywhere can also catch unrelated sources (for example any domain containing “ai”). An anchored list of exact hostnames is more precise. Check your own referral report for new hostnames monthly. Practitioner practice
Limitations
| Gap | Why | Workaround |
|---|---|---|
| AI Overviews / AI Mode clicks | Reported as google / organic | Search Console Generative AI report[2] |
| Copilot inside Bing | Often reported as bing / organic | Bing AI Performance report[3] |
| Apps without referrers | Show as direct | Watch landing pages with sudden direct spikes |
| Mentions without clicks | No visit happens | Prompt panels (measurement) |
ChatGPT appends utm_source=chatgpt.com to referred links, which GA4 records as the session source.[4]
Google's own AI assistants example
Google Analytics Help includes an example custom channel group for AI assistants. Its regular expression for the Source condition is ^.*ai|.*\.openai.*|.*chatgpt.*|.*gemini.*|.*gpt.*|.*copilot.*|.*perplexity.*|.*google.*bard.*|.*bard.*google.*|.*bard.*|.*.*gemini.*google.*$.[1] Google also says to place the new channel above Referral, because the first channel that matches a session wins.[1] The first alternative is very broad, so check your own source list for unrelated matches before trusting totals. Vendor-documented
Limits to plan around
- A standard property can have 2 custom channel groups (5 on Analytics 360), with up to 50 channels per group.[1]
- Custom channel groups apply to historical data as well as new data.[1]
- They are not available in the Key events paths report or in the BigQuery export, so exported data needs its own classification logic.[1]
Vendor-documented
The October 2026 ChatGPT referral gap
OpenAI says ChatGPT adds utm_source=chatgpt.com to referral links.[4] In October 2026 that tag appeared to disappear. Search Engine Land, on October 20, 2026, reported that Adobe's Cedric Huesler compared October 9 to 13 with the preceding week on about 500 pages where ChatGPT normally brought at least 5% of visits: ChatGPT-attributed traffic fell by about 31,000 visits per day while direct traffic rose by about 26,000 on the same pages.[5] OpenAI confirmed to Huesler on October 14 that the missing parameters were a known bug. A fix began rolling out on October 15, and by 9 a.m. Pacific that day tagged ChatGPT clicks had recovered to about 95% to 100% of the previous week's level at the same hour.[5]
The advice in the report is to annotate October 8 to 15 in GA4, avoid changing attribution models because of the dip, and keep UTM tagging because referral information is still missing from most ChatGPT clicks.[5] The lesson for measurement: when a channel falls and direct traffic rises at the same time, check for a tracking change before concluding that visits fell. See measuring AI visibility.
Frequently asked questions
Why does ChatGPT traffic show as direct?
Some app and copy-paste visits send no referrer. Links clicked in ChatGPT usually carry utm_source=chatgpt.com.
Can GA4 show AI Overview traffic?
No. It arrives as Google organic. Use Search Console's Generative AI performance report.
Why did ChatGPT referrals drop in GA4 in October 2026?
Search Engine Land reported that ChatGPT links stopped carrying the utm_source=chatgpt.com parameter, so some visits were counted as direct. OpenAI confirmed a bug and began a fix on October 15, 2026.
See also
References
Pages accessed September 28, 2026 unless a date is given. Sources added on October 31, 2026 were accessed that day. See all sources and our editorial policy.
- ^ "Custom channel groups (includes an “AI assistants” example)". Google Analytics Help.
- ^ "Generative AI performance report (Search)". Search Console Help. Rolled out to all sites by August 31, 2026.
- ^ "Introducing AI Performance in Bing Webmaster Tools Public Preview". Bing Webmaster Blog. Published February 10, 2026.
- ^ "Publishers and Developers – FAQ". OpenAI Help Center.
- ^ "ChatGPT drop in UTM tracking was a bug". Search Engine Land. Published October 20, 2026.