How to Track AI Referral Traffic in GA4 (ChatGPT, Perplexity, Copilot, Gemini)

In this article

1. Why AI referral traffic is worth tracking separately
2. How AI traffic shows up in GA4 today
3. Step by step: create an "AI Assistants" custom channel
4. The reports to build
5. Estimating the AI traffic GA4 can't see
6. What to do with the numbers
7. Frequently asked questions

Why AI referral traffic is worth tracking separately

AI assistants send fewer visits than Google, but the visitors they send have usually done their research already. By the time a buyer clicks a link in a ChatGPT answer, the assistant has often compared vendors and summarized pricing for them. When Ahrefs measured its own site, visitors from AI search converted at 23 times the rate of traditional organic visitors.

If that traffic is spread across Referral, Direct and Unassigned, you can't see it, report on it or connect it to leads. A dedicated channel answers the questions leadership asks: how much traffic AI sends, which assistants send it, which pages it lands on, and whether it converts.

How AI traffic shows up in GA4 today

Every AI platform behaves a bit differently, and GA4 labels traffic by the signals it receives: the referrer header and any UTM parameters in the URL.

What GA4's built-in AI Assistant channel does

Since May 2026, GA4's default channel group has included an AI Assistant channel. Google defines it as traffic "from sources like ChatGPT, Gemini, Deepseek, Copilot, or Grok". When the referrer matches Google's list of AI assistants, GA4 sets the medium to ai-assistant and the campaign to (ai-assistant), and the channel includes any session with that medium.

It's a good start, with three gaps:

• The source list isn't published. You can't be sure every assistant your buyers use (Perplexity and Claude in particular) is on it.
• UTM parameters take priority over the referrer. If a URL has any UTM parameter, GA4 classifies the visit by the UTM values. A link with utm_source=chatgpt.com and no utm_medium can end up in Unassigned instead of AI Assistant.
• No referrer means no attribution. The ChatGPT mobile apps usually open links in the phone's browser, and the referrer is often lost on the way. Without a UTM tag, the visit is counted as Direct.

Step by step: create an "AI Assistants" custom channel

A custom channel group fixes the first two gaps. You need Editor access or higher to the GA4 property.

1. In GA4, go to Admin → Data display → Channel groups.
2. Find the Default channel group and choose Copy to create new. Name the copy something like "Channels incl. AI".
3. Click Add new channel and name it AI Assistants.
4. Add the first condition: Source → matches regex → paste the regex below.
5. Click Or and add a second condition: Medium → exactly matches → ai-assistant. This keeps everything the built-in channel catches.
6. Save the channel, then drag AI Assistants above Referral (and above Unassigned). GA4 assigns each session to the first channel whose rules it matches, so if Referral comes first, perplexity.ai will still be counted as Referral.
7. Save the group. It applies retroactively, so past data is reclassified in reports right away.

Source regex for the AI Assistants channel

^(.*\.)?(chatgpt\.com|chat\.openai\.com|openai\.com|perplexity\.ai|claude\.ai|gemini\.google\.com|bard\.google\.com|copilot\.microsoft\.com|copilot\.com|chat\.deepseek\.com|deepseek\.com|grok\.com|meta\.ai|chat\.mistral\.ai|you\.com)$|^(chatgpt|perplexity|claude|gemini|copilot)$

The first part matches the domains AI platforms send as referrers, including subdomains such as www.perplexity.ai. The second part catches bare UTM values, such as utm_source=chatgpt, that some tools use. Review your Referral report once a quarter and add any new AI domains you find.

The reports to build

Once the channel group exists, you can select it in any standard report or exploration.

• Reports → Acquisition → Traffic acquisition: change the primary dimension to Session custom channel group ("Channels incl. AI"). This is your headline view: AI sessions, engagement rate and key events next to every other channel.
• Which assistants: add Session source as a secondary dimension and filter to the AI Assistants channel.
• Which pages: in Explore → Free form, use Landing page + query string as rows, the custom channel as a filter, and sessions and key events (form submissions, demo requests) as values. These are the pages AI assistants recommend. Keep them accurate and up to date.
• Pipeline: if leads go to a CRM, pass the session source into a hidden form field, as our own forms do with UTM parameters, so sales can see which deals started in ChatGPT.

Estimating the AI traffic GA4 can't see

Some AI-referred visits will always show up as Direct or Organic Search. You can't label them visit by visit, but you can spot the trend:

• Direct traffic to deep pages. People rarely type /industries/aerospace-machining into a browser. A steady rise in Direct landings on product, pricing or comparison pages is often AI app traffic.
• Search Console vs GA4. Clicks from AI Overviews and AI Mode are included in Search Console's Web search data. Pages whose impressions rise while clicks fall are often being answered in an AI Overview.
• Ask. Add "How did you hear about us?" to your demo or quote form, with ChatGPT and other AI assistants as options. It's the only way to capture buyers who researched in AI and then searched for your name.
• Server logs or Cloudflare. AI Crawl Control's Metrics tab includes referral analytics, which gives a second count to compare with GA4.

What to do with the numbers

AI referral traffic is a lagging indicator. It grows after assistants start citing you, which depends on whether their crawlers can reach you, whether your pages state facts plainly, and whether other sites back up what you say. If AI referrals are close to zero, check access first: run the free LLM Readiness Check and review your Cloudflare settings. Then track the channel monthly alongside a visibility measure, such as how often you're named across a fixed set of buyer prompts. The Agent Visibility Score in our audits pairs these two numbers.

Frequently asked questions

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