How to track ChatGPT, Gemini and Perplexity traffic in GA4

GA4 picks a visit's channel from its source and medium. When the referrer is on Google's list of AI assistants, GA4 sets the medium to ai-assistant and the visit lands in the AI Assistant channel. A visit from an assistant off the list stays in Referral, and a visit with no referrer lands in Direct. So the AI Assistant row is a floor, and the number in the board deck needs two more signals next to it.

At martechdevs, we add this as part of GA4 and tracking implementations, next to the server-side tagging and conversion work. Everything below runs in your own GA4 property and CRM.

Does GA4 track ChatGPT traffic?

Yes. Google's channel definitions describe AI Assistant as the channel for visits from sources like ChatGPT, Gemini, DeepSeek, Copilot and Grok (Google Analytics Help). A visit lands there when its medium is exactly ai-assistant, or when its referrer matches Google's list of AI assistants. In that case GA4 sets the medium to ai-assistant and the campaign to (ai-assistant).

Google doesn't publish the full list. It says the definitions may change as the market changes, and that it reviews requests to add sources at least once a year. Clicks from Google's own AI Overviews and AI Mode are left out and count as Organic Search.

Where do you see AI traffic in GA4?

1. Open Reports, then Acquisition, then Traffic acquisition. The table groups sessions by channel.
2. Find the AI Assistant row. If it isn't there, no session matched in that date range.
3. Change the dimension to Session source / medium and search for ai-assistant to see which assistant sent each session.
4. Add your key events as columns, so signups or purchases from AI traffic sit next to the sessions.
5. Open Engagement, then Landing page, and filter on session source to see which pages AI tools send people to.

Those landing pages are the ones AI answers cite. Check them first: is every fact current, does the page say what you sell, and is there a next step?

How do you catch the AI tools GA4 doesn't classify?

Add a custom channel group with an AI channel above Referral. Custom channel groups apply to past data in reports, so the history fills in as soon as you save. Google's own help page uses AI assistants as its example and names ChatGPT, Gemini, Microsoft Copilot, Claude and Perplexity (Google Analytics Help).

1. In Admin, under Data display, open Channel groups. You need Editor access on the property.
2. Click Create new channel group. It starts as a copy of the default group.
3. Click Add new channel, name it AI assistants, and add a condition: Source matches regex, with the pattern below.
4. Click Save channel, then Reorder. Drag AI assistants above Referral and click Apply.
5. Save the group. In Traffic acquisition, switch the primary dimension to your new channel group.

.*(chatgpt|openai|perplexity|claude\.ai|gemini\.google|copilot|deepseek|grok|meta\.ai|mistral).*

Keep the pattern in a doc and update it when a new assistant starts sending traffic. A standard GA4 property allows two custom channel groups and GA4 360 allows five, with up to 50 channels in each.

For a quick look without changing settings, build a Free-form exploration with Session source as the row and a filter on Session source matching the same pattern.

What does GA4's AI Assistant channel miss?

Most of the influence. Profound tracked brand site visits after AI mentions across more than 2 million conversations from January to June 2026. Visits ran 1.5 to 2.5 times the expected baseline over the next 7 days, over 97% of them carried no UTM, and in June 2026 about 2.5% of ChatGPT visits had a trackable AI referral parameter (Profound, July 2026).

• AI Overviews and AI Mode: Google counts these clicks as Organic Search, and Search Console reports them inside Web performance (Google Search Central).
• People who read the answer and come back later: they search your name or type your URL, so the visit lands in Organic Search or Direct.
• Links copied out of the chat: a pasted link arrives with no referrer and lands in Direct.

How do you measure the AI traffic GA4 can't see?

Use three signals together and report them side by side.

1. The AI Assistant channel, or your custom AI channel, for sessions and key events you can attribute directly.
2. A "How did you hear about us?" field on signup and demo forms, with ChatGPT, Perplexity, Gemini, Claude and Google's AI results as options. Store the answer as a property in HubSpot or Salesforce, so it travels with the deal.
3. Pipeline by that property in the CRM, so the board sees AI-influenced revenue next to AI-referred sessions.

In Mixpanel or PostHog, the initial referring domain does the same job as GA4's source. Filter it with the same list of domains.

Is AI traffic worth tracking?

It is small, and it converts. BrightEdge data put ChatGPT at 95.1% of AI referral traffic to websites in August 2026, with Gemini at 2.4%, Perplexity at 1.1% and Claude at 0.8% (The Next Web, September 2026).

• Ahrefs found AI search sent 0.5% of its visits but 12.1% of its signups, about 23 times the conversion rate of organic search. That's one site's data (Ahrefs, June 2025).
• Semrush reports the average AI search visitor is worth 4.4 times a traditional organic visitor on conversion rate. It's a vendor figure, and the raw rates weren't published (Semrush, July 2025).
• HubSpot surveyed more than 3,000 CRM buyers and found 42% used AI search during evaluation, and those buyers were 36% more likely to purchase (HubSpot, January 2026).

If AI answers already send you signups, keep the pages they cite current. AI answers lag on renamed products and changed prices, and a stale page is what they quote.

What does this look like for a 20-person SaaS?

An example setup for a 20-person B2B SaaS on GA4 and HubSpot, in the order we would run it. The numbers will be yours.

1. Day one: check Traffic acquisition for the AI Assistant row and note the top five landing pages from it.
2. Same day: add the custom AI channel group above Referral and compare it with the default channel. The gap is AI traffic GA4 files as Referral.
3. Week one: add "How did you hear about us?" to the demo form, map it to a HubSpot contact property and copy it to the deal.
4. Month one: report sessions, signups and pipeline by AI source in one view, and review the pages AI tools cite.