How to track AI referral traffic in GA4

AI referral traffic is visits that start when someone clicks a link in an AI assistant's answer. In Google Analytics 4 (GA4), check the AI Assistant channel that Google added on May 13, 2026 (opens in a new tab), then create a custom channel group with a channel that matches assistant sources such as chatgpt.com, put it above Referral, and read it in the Traffic acquisition report. GA4 cannot see answers that produce no click, or clicks that arrive without a referrer.

Referral visits are one input to measuring AI visibility, and a small one: in a February 2025 study of 3,000 sites, 0.17% of the average site's visitors came from AI chatbots (opens in a new tab) (vendor study). This guide sets GA4 up to count those visits as completely as it can and says plainly what it cannot count. Every GA4 step follows Google's Analytics Help pages as they read on September 27, 2026. GA4's menus change, so each step links the help page to check against.

Scope and definitions

AI referral traffic is one outcome of answer engine optimization (AEO), the work of getting a company cited in AI answers. This guide covers GA4 on websites and clicks from the assistants' own sites and apps, such as ChatGPT, Claude, Perplexity, Gemini, Copilot, DeepSeek, and Grok. Clicks from Google's AI Overviews and AI Mode are not AI referral traffic in GA4's terms: GA4 counts them as Organic Search (opens in a new tab), and they are measured in Search Console instead.

• Source is the "specific platform, website, app, or online location that referred a user" (opens in a new tab), for example chatgpt.com.
• Medium is the type of traffic, such as "organic," "cpc," "referral," or "none" (opens in a new tab).
• A session is the period from when a user visits your website to when they leave (opens in a new tab).
• Channels are rule-based definitions of your website's traffic sources (opens in a new tab). The default channel group is Google's set of channels, and it can't be edited (opens in a new tab). A custom channel group is your own set of rule-based categories (opens in a new tab).
• The referrer is the address of the page a visitor came from. When a user clicks a link, the browser "will often send a Referer: header" (opens in a new tab) with the request. GA4 stores it in the Page referrer dimension, the "referring URL, which is the user's previous URL" (opens in a new tab).
• UTM parameters are tags added to a link's address, such as utm_source, that GA4 reads to fill in the source, medium, and campaign (opens in a new tab).
• A key event is an event you mark as important, such as a form submission or a purchase, so that you can evaluate the channels that lead people to take it (opens in a new tab).

How GA4 classifies a visit from an AI assistant

GA4 collects website data through the Google tag, which is set up with the gtag.js JavaScript framework or Google Tag Manager (opens in a new tab). Each page view carries the page's full address, including any UTM parameters, and the referrer. GA4 turns those into a source, a medium, and a channel by these rules (all official documentation):

1. UTM parameters come first. When the landing page's address carries campaign parameters, GA4 processes the session as a custom campaign, and "the values of the custom-campaign parameters map directly to the dimensions in reports." (opens in a new tab) The referrer "may set dimensions when no other campaign or traffic source fields have been set." (opens in a new tab) Missing UTM parameters "will result in (not set) values" (opens in a new tab).
2. Recognized AI assistants get their own medium. Since May 13, 2026, the medium "ai-assistant" is "automatically assigned when the referrer matches a recognized AI Assistant," the campaign is set to "(ai-assistant)," and the visit goes into the AI Assistant channel (opens in a new tab).
3. Google names some of those assistants, not all. The channel description says users "arrive at your site from sources like ChatGPT, Gemini, Deepseek, Copilot, or Grok" (opens in a new tab), and the release note names ChatGPT, Gemini, and Claude (opens in a new tab). Perplexity is named in neither. The rule refers to "a list of AI Assistants" (opens in a new tab), but the downloadable list of sources linked from the channel page (opens in a new tab) has only search, shopping, social, and video categories (checked September 27, 2026).
4. Other links from websites are Referral. Referral is the channel for "non-ad links on other sites/apps," and its rule is that the medium is "referral," "app," or "link" (opens in a new tab).
5. Google's own AI features are search. Organic Search includes "Google's AI Overviews and AI Mode" (opens in a new tab).
6. No information means Direct. A session is processed as direct "when no information about the referral source is available" (opens in a new tab).
7. Anything else is Unassigned. Unassigned "is the value Analytics uses when there are no other channel rules that match the event data." (opens in a new tab)
8. A session keeps one source. Each session "is associated with only one campaign or traffic source," and "a direct-traffic visit that follows a referred visit will never override an existing referrer." (opens in a new tab)

A separate dimension added on June 11, 2026, Source group, consolidates source values and "includes built-in grouping for emerging traffic sources like ChatGPT (OpenAI) and Perplexity" (opens in a new tab). Google describes it as part of cross-channel reporting in the Advertising section, not as a channel.

What this means for ChatGPT links

OpenAI says ChatGPT "automatically includes the UTM parameter utm_source=chatgpt.com in referral URLs" (opens in a new tab). Under rule 1, such a visit gets the source chatgpt.com. OpenAI documents only that one parameter, so under Google's general rule the medium would be (not set). Google's help pages do not say whether the AI Assistant rule still applies when a link carries a UTM parameter. If it does not, no default rule matches chatgpt.com with a medium of (not set), and the visit would be labeled Unassigned. This is our reading of the documentation, not a tested result. Step 1 below shows how to see which happens in your property.

Where AI-related visits usually land

What GA4 cannot see

• Answers without a click. GA4 records visits, not answers. Google users who saw an AI summary clicked a link in the summary itself in just 1% of visits (opens in a new tab) (Pew Research Center; 900 U.S. adults, March 2025). First-party counts of AI appearances come from the search engines' own tools: Bing Webmaster Tools reports citations in Copilot and Bing's AI summaries (opens in a new tab), and Search Console reports impressions in AI Overviews and AI Mode (opens in a new tab).
• Clicks without a referrer. Traffic referred by Claude's native app does not include a Referer header, and Cloudflare believes the same holds for other native apps (opens in a new tab) (network measurement). Such visits count as Direct. In a small test in early 2025, visits from links in Copilot were recorded as Direct in Ahrefs' analytics, after Copilot referrals dropped around October 2024 (opens in a new tab) (vendor test; Copilot may have changed since).
• Which Google search clicks came from AI features. Clicks from AI Overviews and AI Mode count as Organic Search (opens in a new tab), and Search Console includes them in the Performance report under the "Web" search type (opens in a new tab), mixed with other search clicks.
• Assistants reading your pages. When a person asks ChatGPT a question, it "may visit a web page with a ChatGPT-User agent" (opens in a new tab), and Anthropic's Claude-User (opens in a new tab) and Perplexity's Perplexity-User (opens in a new tab) do the same. In Vercel's December 2024 data, none of the major AI crawlers rendered JavaScript, including ChatGPT-User (opens in a new tab), so these fetches do not run the Google tag. They appear only in server logs.
• Influence that arrives later through another channel. In one agency's records, 189 of 213 leads named an AI tool when asked how they heard of the agency, but first-touch attribution credited AI with only 28 of those 189; 95 were filed under Organic Search and 59 under Direct (opens in a new tab) (single firm; the agency sells AEO services).
• Visitors who decline analytics cookies. With consent mode, the basic setup sends Google no data at all when a visitor does not consent, while the advanced setup sends "measurements without cookies" (opens in a new tab), and Google models the gaps only when the tag meets "a certain data collection threshold" (opens in a new tab). AEO HQ's own site, for example, sets analytics cookies only after a visitor accepts them.
• The source of visits from people using ad blockers. Google says ad blockers "can interfere with tracking cookies used to identify the traffic origin," so the traffic is classified as (direct) / (none) (opens in a new tab).

Steps

Each step below follows the Google help page it links, as read on September 27, 2026. The recommendations are AEO HQ's and are marked as such.

1. See what GA4 already records

Open the Traffic acquisition report: from the left menu, select Reports, then Acquisition, then Traffic acquisition (opens in a new tab). Its default dimension is the session default channel group (opens in a new tab), so look for an AI Assistant row. Then switch the table's dimension to Session source / medium and use the search bar above the table (opens in a new tab) to look for chatgpt, perplexity, claude, gemini, copilot, deepseek, and grok. Write down every combination you find and its channel. If the report is missing, Editors and above can add it back to the left navigation (opens in a new tab).

2. List the assistant sources you will count

The table lists the web address each assistant's company uses, from its own documentation. None of these companies documents the exact referrer its links send, and a referrer can differ, for example by a "www." prefix. Treat the list as examples to check against step 1, and add any other assistant you find there.

3. Create a custom channel group

In Admin, under Data display, click Channel groups, then Create new channel group (opens in a new tab). The new group starts as a copy of the default group (opens in a new tab). You need the Editor role or above (opens in a new tab). Give the group a name, such as "Channels with AI assistants." A standard property can have 2 custom channel groups in addition to the default, with up to 50 channels in each (opens in a new tab).

4. Add a channel for AI assistants

Click Add new channel, name it, and click Add condition group (opens in a new tab). Name the channel "AI assistants." For the condition, choose Source and "matches regex," which Google's own AI assistants example uses (opens in a new tab), and enter a pattern built from your list in step 2. With the addresses above, the pattern is:

^(.*\.)?(chatgpt\.com|perplexity\.(ai|com)|claude\.(ai|com)|gemini\.google\.com|copilot\.microsoft\.com)$

How the pattern works:

• Whole-value matching. Google Analytics uses "full regex" by default, so an expression without metacharacters "only returns exactly matching values." (opens in a new tab) The ^ and $ state that explicitly.
• Literal dots. A backslash before a dot means the dot is "interpreted as a period" rather than as a wildcard (opens in a new tab).
• Subdomains. (.*\.)? also matches the same address with a prefix such as "www.".
• Source, not medium. The condition is on the source, so it catches chatgpt.com whether its medium is ai-assistant, referral, or (not set).

Google's help page offers its own example pattern for this channel. It begins with ^.*ai|, which matches any source that ends in "ai", such as any site on a .ai domain, so it can count ordinary referrals as AI traffic (our reading of the pattern). We recommend listing domains instead, as above. Google also advises that you "update your regex expression if URLs or the list of assistants you wish to measure change." (opens in a new tab)

Then check whether your copied group already has a channel named AI Assistant. If it does not, add one with the condition Medium exactly matches ai-assistant, which is how Google defines its AI Assistant channel (opens in a new tab). That channel catches assistants that Google recognizes but your pattern does not list. This second channel is our recommendation, not a Google instruction.

5. Put the AI channels first and save

Traffic "is included in the first channel whose definition it matches given the current order of channels in the group." (opens in a new tab) Google's example says to move the AI assistants channel above Referral, and above other channels such as Organic Search if needed (opens in a new tab). Click Reorder, drag the channels, click Apply, and then click Save group (opens in a new tab). Place your "AI assistants" channel first and the AI Assistant channel second.

6. Read the results

Return to Traffic acquisition and choose your new channel group as the table's dimension. Google says custom channel groups can be used as the primary dimension in reports that support the default channel group, such as the Acquisition reports (opens in a new tab), and that they can be applied to your reports retroactively (opens in a new tab), so earlier data is regrouped too.

For more detail, open Explore and select the Free form template (opens in a new tab). Useful dimensions are your channel group, Session source / medium, Landing page + query string, and Page referrer. UTM parameters are left out of Landing page + query string and appear in the Page location dimension instead (opens in a new tab). Useful metrics are Sessions, Engaged sessions, and Key events. GA4 counts an engaged session as one that "lasted 10 seconds or longer, or had 1 or more key events or 2 or more page or screen views" (opens in a new tab).

You can also make the new group your property's primary channel group. Any custom channel group can be selected as the primary channel group in Admin, under Channel groups, and data "will populate using the new criteria from that point forward." (opens in a new tab) Unlike the custom group itself, that change is not applied to past data.

7. Mark the actions that matter as key events

In Admin, under Data display, click Events, find the event, and click the star icon to mark it as a key event (opens in a new tab). Mark lead forms, sign-ups, and purchases. A standard property can mark up to 30 events as key events (opens in a new tab). Marking an event as a key event "affects reports from time of creation. It doesn't change historic data." (opens in a new tab) The Traffic acquisition report then shows Key events and Session key event rate, "the percentage of sessions in which a user triggered a key event" (opens in a new tab), for each channel.

8. Keep enough history for explorations

A standard property keeps user-level data and key events for 2 or 14 months, and other event data for 2 or 14 months (opens in a new tab). The setting "does not affect standard aggregated reports" and "only affects explorations and funnel reports." (opens in a new tab) We recommend 14 months, so that explorations can compare a month of AI traffic with the same month a year earlier. You need the Editor role (opens in a new tab) to change the property's Data retention setting.

9. Review the channel every month

Look in Referral and Unassigned for new assistant sources, compare your "AI assistants" channel with GA4's AI Assistant channel, and update the pattern when you find a new source (recommendation). Two cautions from Google: custom channel group deletions "are irreversible," (opens in a new tab) and custom channel groups "aren't available in the BigQuery Export Schema," (opens in a new tab) so if you analyze exported data, repeat the same rules in your queries.

10. Add the data GA4 cannot provide

GA4 answers one question: who clicked through. To cover the rest (recommendations):

• Ask buyers. Add "Where did you first hear about us?" to sign-up and checkout forms. Ahrefs reported more than 14,000 new users who said ChatGPT sent them (opens in a new tab), collected through a registration question (vendor data).
• Use the search engines' reports. Search Console's generative AI performance report counts impressions in AI Overviews and AI Mode (opens in a new tab), and Bing Webmaster Tools' AI Performance report shows citations for Copilot and Bing's AI summaries (opens in a new tab), with a sample of the grounding queries behind them. How to combine them with a prompt panel is covered in how to measure AI visibility.
• Read your server logs for ChatGPT-User, Claude-User, and Perplexity-User requests by URL. The agents are listed in the glossary under OpenAI crawlers, Anthropic crawlers, and Perplexity crawlers.
• Check your CRM's source field. HubSpot's Original Source, for example, is a first-touch model (opens in a new tab). AEO for HubSpot users covers the HubSpot side.
• Define the metrics once. Referral sessions and key events from AI assistants are two of the measures defined in AEO metrics and KPIs.

What the evidence shows and does not show

Antipatterns

An antipattern is a practice that looks helpful but fails or backfires.

1. Relying only on the default AI Assistant channel. Its description does not name Perplexity (opens in a new tab), and its handling of UTM-tagged ChatGPT visits is not documented. Instead, add a custom channel defined by source.
2. Defining the AI channel by medium alone. Missing UTM parameters produce (not set) values (opens in a new tab), so a medium-only rule can miss chatgpt.com visits. Instead, match on source.
3. Copying Google's example pattern unchanged. It begins with ^.*ai|, which matches any source ending in "ai". Instead, list the assistant domains.
4. Placing the AI channel below Referral. Traffic goes to the first channel it matches (opens in a new tab). Instead, put the AI channels first.
5. Expecting AI Overviews in the AI channel. They count as Organic Search (opens in a new tab). Instead, use Search Console's generative AI performance report (opens in a new tab).
6. Treating AI referrals as the whole effect. Links inside Google's AI summaries were clicked on 1% of visits (opens in a new tab), and first-touch attribution caught 15% of self-reported AI leads at one agency (opens in a new tab). Instead, combine referrals with self-reported source, search engine reports, and a prompt panel.

Checklist

FAQ

Why does ChatGPT traffic show as (not set) or Unassigned in GA4?

ChatGPT adds utm_source=chatgpt.com to referral URLs (opens in a new tab) but, as documented, no medium, and missing UTM parameters produce (not set) values (opens in a new tab). A visit with no matching channel rule is labeled Unassigned (opens in a new tab). A custom channel that matches on the source chatgpt.com collects these visits whatever their medium.

Does GA4 track Perplexity and Claude?

GA4 records their visits, but its channel description does not name Perplexity (opens in a new tab), and only the release note names Claude (opens in a new tab). Visits from them may land in AI Assistant, Referral, or Direct. The custom channel in steps 3 to 5 groups them explicitly. In one mostly B2B panel, Claude and Perplexity together sent about a quarter of measurable AI referrals in March–April 2026 (opens in a new tab) (vendor panel).

Where do AI Overviews and AI Mode clicks appear in GA4?

In Organic Search, with other Google search clicks. GA4's Organic Search channel includes them (opens in a new tab). Search Console's generative AI performance report shows their impressions (opens in a new tab), and the AI Overviews guide covers them in detail.

Will a new channel group change my historical reports?

A custom channel group can be applied to your reports retroactively (opens in a new tab). Making it the primary channel group is different: data populates with the new criteria "from that point forward." (opens in a new tab) The default channel group itself can't be edited (opens in a new tab).

Can GA4 show which AI answer mentioned my company?

No. GA4 records visits, their source, and the "referring URL" (opens in a new tab), not the conversation that led to the click. Bing Webmaster Tools shows a sample of the grounding queries behind citations in Copilot and Bing's AI summaries (opens in a new tab), and a prompt panel shows the answers themselves.

Is AI referral traffic worth more than other traffic?

The evidence is contested. A peer-reviewed study of 973 e-commerce sites from August 2024 to July 2025 found ChatGPT referrals converted below organic search, paid search, email, and affiliate traffic, and above paid social only (opens in a new tab). Its data came from the first author's employer, and it used last-click attribution, which the authors note cannot capture upper-funnel contributions (opens in a new tab). Mark your own key events and compare channels with enough sessions to be meaningful.

How much AI referral traffic is normal?

Across 3,000 sites in early 2025, AI chatbots sent 0.17% of the average site's visitors (opens in a new tab), and the smallest sites got a higher share, 0.56% of visitors for sites under 1,000 monthly visitors (opens in a new tab) (vendor study). Shares have shifted since: in one B2B panel, ChatGPT's share of AI referrals fell from 89.1% to 62.6% between mid-2025 and March–April 2026 (opens in a new tab) (vendor panel).

Should I also use Microsoft Clarity?

It can serve as a cross-check. Clarity's AIPlatform channel covers sessions from the standalone sites of Claude, Copilot, Gemini, ChatGPT, and Perplexity (opens in a new tab). It has the same blind spots: hidden sources "might appear as Direct," and AI features embedded in search engines are not included (opens in a new tab).

Next steps

AEO HQ's Instant AEO Audit ($499) checks a site's crawler access, key pages, and structured data automatically. It does not use your analytics data. The methodology page lists what it measures and what it does not.

Change log

• September 28, 2026: First published.