How to track AI traffic in GA4: ChatGPT, Perplexity, Gemini and Copilot

How to track AI traffic in GA4: the short answer

Start with the AI Assistant channel that GA4 now has, then check the session source values underneath it. Google's help page defines the channel as visits from sources like ChatGPT, Gemini, DeepSeek, Copilot or Grok, and says it excludes Google's AI Overviews and AI Mode (Google Analytics help).

In practice, open Reports, then Acquisition, then Traffic acquisition. Set the table to Session default channel group and look for AI Assistant. Then switch the dimension to Session source and search for the domains in the table below. That second step catches any assistant the channel does not cover.

A visit is only counted as AI traffic when the browser tells GA4 where it came from. It does that in two ways. One is the referrer, a header the browser sends naming the site the visitor clicked from. The other is a utm_source tag, a label added to the end of the link itself. When neither arrives, GA4 has nothing to go on and files the visit as Direct.

Every AI traffic figure in GA4 is a floor. It counts the visits that arrived labelled, and some never are.

How each assistant shows up in your reports

Each assistant leaves a different trace. The table lists what each one sends, with the public source for each claim, and says plainly where we could not find a source to verify it.

ChatGPT is the best documented. OpenAI's publisher FAQ said that ChatGPT automatically includes the UTM parameter utm_source=chatgpt.com (OpenAI help, archived 4 October 2026). Seer Interactive's published test adds a caveat: ChatGPT's citation links usually carry the tag, while some of its search result links did not (Seer Interactive).

Perplexity, Gemini and Claude send a referrer but, in Seer's test, no utm tag by default. GA4 recorded them with sources perplexity.ai, gemini.google.com and claude.ai and a medium of referral (Seer Interactive).

Copilot is the weakest row. One analytics blog lists copilot.microsoft.com as its referrer (Nice Looking Data), but its author says the piece documents expected behaviour rather than a test, and we found no Microsoft page that states it. Treat it as unverified. Google's channel does name Copilot as an AI Assistant source, so its visits should land in that channel whatever the exact domain.

What the AI Assistant channel in GA4 does

The AI Assistant channel is a ready-made bucket in GA4's default channel group, so you no longer need to build one to see most AI visits. Google says a visit is placed there when its medium exactly matches ai-assistant, or when its referrer matches a list of AI assistants (Google Analytics help).

Three details decide how far you can trust it. First, Google does not publish the full list of referrers behind the channel on that page. It names examples: ChatGPT, Gemini, DeepSeek, Copilot and Grok. Perplexity and Claude are not among them, so check where your perplexity.ai and claude.ai sessions land before assuming they are counted. Second, it excludes Google's own AI Overviews and AI Mode, which Google files under Organic Search. Third, a channel is a label applied to visits, so it cannot see a visit that arrived with no referrer.

The medium rule is worth knowing for your own links. If you tag a link yourself with utm_medium=ai-assistant, Google's rule says GA4 will put that visit in the channel. Only do this for links that really sit inside an assistant, or the channel will count visits that never came from one.

Building your own AI traffic channel

Build your own channel only if the default one misses a source you care about, such as Perplexity. A custom channel group lets you write the rule yourself, and Google says it applies to your reports retroactively (Google Analytics help).

1. In GA4, open Admin, then Data display, then Channel groups. You need the Editor role or above on the property.
2. Click Create new channel group. GA4 starts you with a copy of the default group, which keeps every other channel working.
3. Add a new channel and name it something plain, such as AI assistants.
4. Set its condition to Source matches regex, and paste a pattern of the domains you want, such as the one in the table below.
5. Move the new channel above Referral in the list. Google says traffic goes into the first channel whose rule it matches, so a channel placed below Referral would never receive these visits.
6. Save the group, then choose it as the dimension in Traffic acquisition and compare it with the default AI Assistant channel.

Google allows a standard property 2 custom channel groups and a 360 property 5, in addition to the default group, and up to 50 channels in each group (Google Analytics help). Spend one of the two on this only if the default channel genuinely leaves a gap.

AI traffic that arrives with no referrer

Some AI visits arrive with no referrer and no tag, and GA4 counts them as Direct. Nothing in GA4 can move them back, so the honest response is to say the figure is a floor.

There are a few ordinary reasons. A buyer can copy a link out of an answer and paste it into a new tab, which sends no referrer. Seer Interactive lists links clicked inside many mobile apps among the clicks that cannot be tracked. A page can also tell the browser to send none: MDN's reference describes a no-referrer policy that leaves the header out entirely (MDN). Seer Interactive notes that AI traffic without attribution will likely appear as Direct and can inflate that channel (Seer Interactive).

Even when a referrer does arrive, it says very little. Under the browser default, strict-origin-when-cross-origin, a link from one HTTPS site to another sends only the origin, meaning the bare domain (MDN). So GA4 sees chatgpt.com, never the question the buyer asked or the answer they read.

• You can see that a visit came from an assistant, when it is labelled.
• You can see which page it landed on and what the visitor did next.
• You cannot see the question the buyer asked the assistant.
• You cannot see what the answer said about you or your rivals.
• You cannot recover a visit that arrived with no referrer and no tag.

What AI traffic in GA4 cannot tell you

GA4 shows the buyers who clicked. It cannot show the far larger group who read an answer, took its advice and never clicked anything, including every answer that named a rival instead of you.

Google's own AI results add a second blind spot. Google says sites appearing in AI features such as AI Overviews and AI Mode are included in the overall search traffic in Search Console (Google Search Central), and GA4 files those clicks as Organic Search. You cannot split them out in either tool.

So treat traffic and answers as two different measurements. Traffic tells you what happened after a click. To know what the assistants say before anyone clicks, you have to ask them and keep the answers, which is what answer tracking does. Agentcites measures that side only. It asks ChatGPT, Perplexity, Gemini and DeepSeek your buyer questions every week and keeps every answer, but it does not read your analytics or count visits. Our guide to tracking brand mentions in AI search explains the method.

Checking that your setup works

Check your setup by clicking a real link yourself and watching where the visit lands. It takes a few minutes and tells you more than any list of domains.

1. Ask an assistant a question that it is likely to answer with a link to your site, and click the link.
2. Open the Realtime report in GA4 and look at the source of your own visit.
3. Note whether it shows as AI Assistant, Referral or Direct, and which source value it carries.
4. Repeat on a phone app if your buyers use one, since apps can drop the referrer.
5. Repeat every few months, because platforms change how they link without notice.

If a visit you know came from an assistant shows as Direct, that is the no referrer case described above, and no rule in GA4 will fix it. If it shows as Referral with a recognisable AI domain, add that domain to your custom channel.

Reporting AI traffic honestly

Report AI traffic as sessions from labelled AI sources, with the date range and the rule you used, and say that unlabelled visits are not included. A short note like that stops a reader treating a floor as a total.

• Name the rule. Say whether you used GA4's AI Assistant channel, your own channel, or both.
• Give the count and the base. Write 312 of 48,000 sessions, not 0.65% on its own. Those numbers are a made-up example.
• Report each assistant on its own line, because they send traffic for different reasons.
• Say what is missing. Direct traffic, AI Overviews and AI Mode are not in the figure.
• Compare like with like. If you added a domain to the rule this month, last month's figure used a different rule.

The same rules apply to every AI figure you report, not only traffic. Our guide on reporting AI visibility honestly sets them out with worked examples.