How to track AI referral traffic in GA4

Open Reports, then Acquisition, then Traffic acquisition, and find the AI Assistant row. Since 13 May 2026, GA4's default channel group has put visits referred by AI assistants such as ChatGPT, Gemini and Claude into that channel. Clicks from Google's AI Overviews and AI Mode are not in it: GA4 counts them as Organic Search.

So the basic setup is done for you. What is left is splitting the channel by assistant, catching assistants GA4 does not recognize, and knowing which AI-driven visits never reach GA4 at all. The traffic figures are one input to a wider AI visibility audit, not the whole picture.

How GA4 files AI traffic

When GA4 recognizes an assistant from the referrer, it sets the medium to ai-assistant and the campaign to (ai-assistant). Google's help pages name ChatGPT, Gemini, DeepSeek, Copilot, Grok and Claude as examples but do not print the full list in the text. Step 1 shows you which assistants actually arrive with that medium in your own data.

The default group cannot be edited. To change how AI traffic is grouped, you build a custom channel group, covered in step 2.

Step 1: Read the AI Assistant channel

1. In GA4, open Reports.
2. Select Acquisition, then Traffic acquisition.
3. Leave the table's dimension on Session default channel group and find the AI Assistant row.
4. Compare its sessions, engagement rate and key events with Organic Search over the same dates.
5. Switch the dimension to Session source / medium.
6. Type ai-assistant in the search box above the table to list every assistant that sent visits.

Step 2: Give each assistant its own channel

A custom channel group lets you see ChatGPT, Perplexity and the rest as separate rows. You need the Editor role or above.

1. Go to Admin and, under Data display, click Channel groups.
2. Click Create new channel group. GA4 starts you with a copy of the default group, AI Assistant channel included.
3. Name the group, for example "Channels with AI split".
4. Click Add new channel, name it "ChatGPT", and add the condition Source matches regex .*(chatgpt|openai).*
5. Repeat for each assistant with the patterns below.
6. Click Reorder and drag the new channels above AI Assistant and Referral.
7. Click Save group, then choose the group as the dimension in Traffic acquisition.

Channel      Condition: Source matches regex
ChatGPT      .*(chatgpt|openai).*
Perplexity   .*perplexity.*
Claude       .*claude.*
Gemini       .*gemini.*
Copilot      .*copilot.*
Grok         .*grok.*

Four details decide whether this works:

• Order. GA4 puts each visit in the first channel it matches, reading from the top. A ChatGPT channel placed below AI Assistant would only receive the visits AI Assistant missed.
• Full matching. GA4's regular expressions match the whole value by default, so each pattern starts and ends with .* to let the name appear anywhere in the source.
• False matches. A broad pattern can catch an unrelated site whose domain contains the same word. After a week, check the sources each channel collected and tighten any pattern that caught the wrong site.
• Limits. Custom channel groups apply to past data as well as new data. A standard property can have two custom groups, each with up to 50 channels.

Google's help page on custom channel groups also shows a single "AI assistants" channel with a longer pattern, if you prefer one row to six.

ChatGPT tags its links; others may not

OpenAI says ChatGPT automatically adds utm_source=chatgpt.com to its referral links. GA4 maps campaign parameters in the landing URL straight into its source dimension, so those visits show chatgpt.com as their source.

That only works if the parameter survives the landing. If your site redirects visitors, for example from http to https or to a trailing slash, check that the redirect keeps the query string:

curl -s -o /dev/null -w "%{redirect_url}\n" "https://example.com/pricing?utm_source=chatgpt.com"

The address printed should still end in ?utm_source=chatgpt.com. An empty line means no redirect happened, which is also fine.

We found no documentation of a tracking parameter from Perplexity, so for Perplexity and the other assistants, rely on the referrer and on GA4's AI Assistant list.

What GA4 cannot see

• Visits without a referrer. GA4 processes a session as Direct when no information about its source is available. An AI-driven visit that arrives with no referrer and no campaign parameters lands there, indistinguishable from a typed address.
• Google's AI features. GA4's definitions put clicks from AI Overviews and AI Mode inside Organic Search. For how often your pages appear in those features, use Search Console's Generative AI performance report, explained in how to use Google Search Console for AI search.
• Answers that send no one. GA4 measures visits. An answer that recommends you but produces no click leaves no trace in it, the AI version of a zero-click search. To see those, you need to check the answers themselves, as described in how to measure AI share of voice.

What to do first

• Open Traffic acquisition and note last month's AI Assistant sessions and key events.
• List every source with the ai-assistant medium.
• Build a custom channel group with one channel per assistant, placed above AI Assistant and Referral.
• Test that your redirects keep utm_source=chatgpt.com on the landing URL.
• Pair GA4 with Search Console for Google's AI features and with answer tracking for the answers that send no clicks.