How to see AI traffic in GA4: the new AI Assistants channel, a regex fallback, and what stays invisible

Since May 13, 2026, GA4 sorts recognized AI-assistant clicks — ChatGPT, Gemini, Claude, Copilot — into a native AI Assistants channel. Everything before that date, and anything Google’s unpublished list misses, sits in Referral under sources like chatgpt.com. And Google’s own AI Overviews and AI Mode clicks stay locked inside google / organic, unsplittable. Worth the setup: on Ahrefs’ own site, AI search was 0.5% of traffic but drove 12.1% of signups (Ahrefs) — one company’s number, but small, high-intent, and easy to misattribute.

Which referrer does each AI assistant send?

Each major assistant’s web app announces itself with its own referrer domain — that referrer is the entire basis of AI-traffic tracking in GA4. Here’s the landscape, compiled from Seer Interactive, Swydo, and MarTech:

The utm_source=chatgpt.com tag is observed behavior across multiple independent datasets, not an OpenAI statement — OpenAI’s own publishers FAQ returned HTTP 403 to every fetch we tried, so we can’t cite the primary page. Seer notes the parameter is conditional: applied to cited sources, and generally omitted on privacy-sensitive topics.

The dark-traffic caveat is real. Native desktop and mobile apps and most in-app webviews strip the referrer header, so those sessions land in Direct — as do copy-pasted links (Seer, GA4 Optimizer). Per MarTech’s testing, ChatGPT’s Atlas browser often strips or blocks referrers too, showing up as Direct or “(not set)”. One claim we keep seeing — that free-tier ChatGPT users don’t send referrers — we could not trace to any measurement writeup; everything verified points to the surface (app vs. web), not the plan tier.

What is the new AI Assistants channel in GA4?

On May 13, 2026, Google added a native channel for AI traffic to GA4’s Default Channel Group — the headline change this year for anyone tracking assistant referrals. From the release notes: “You can now identify how users are discovering your site through chatbots like ChatGPT, Gemini, and Claude via a new AI Assistant channel in your Default Channel Group reports.”

Mechanically: 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 session classifies into the channel. Google’s channel-definitions page describes it as “the channel by which users arrive at your site from sources like ChatGPT, Gemini, Deepseek, Copilot, or Grok. It excludes Google’s AI Overviews and AI Mode.”

Two footnotes. Google itself hasn’t settled the name — the release note says “AI Assistant,” the definitions page “AI Assistants.” And Grok is named in Google’s definition, but we found no measurement writeup of Grok’s observed referrer strings — include it in a regex, don’t assume behavior. Medium

What are the native channel’s blind spots?

Three: it isn’t retroactive, the referrer list is unpublished, and Perplexity’s status is unconfirmed.

It’s forward-only. GA4 processes channel data forward, so nothing gets reclassified retroactively — AI sessions from before the rollout stay wherever they originally landed, typically Referral or Direct (GA4 Optimizer). Practitioners had been watching rows like chatgpt.com / referral in that bucket for years (Lawrence Hitches), and that’s where your history stays.

Rollout timing is fuzzier than the announcement date suggests: announced May 13, 2026, it rolled out gradually over the following weeks. Third parties reported broad availability around June 2026, but we found no Google statement confirming completion. Medium

And Perplexity: Google’s example list (“sources like…”) is explicitly non-exhaustive, and the full referrer list is unpublished. As of early July 2026 Perplexity isn’t named in the docs, and practitioners report it still classifying as Referral — unconfirmed either way, so check your own property. Low

How do you build the regex fallback with a custom channel group?

Create a custom channel group with an “AI assistants” channel that matches session source against a regex of assistant domains, then reorder it above Referral — Google’s custom channel group documentation walks through exactly this case. It even supplies an example regex, verbatim:

^.*ai|.*\.openai.*|.*chatgpt.*|.*gemini.*|.*gpt.*|.*copilot.*|.*perplexity.*|.*google.*bard.*|.*bard.*google.*|.*bard.*|.*.*gemini.*google.*$

We’d tighten that. The ^.*ai branch matches any source ending in “ai” — every .ai domain on the web — and .*gpt.* catches anything containing “gpt”. Practitioner regexes are domain-anchored instead; synthesizing Swydo and Analytics Mania:

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

Why bother now that a native channel exists? Because per Google’s own doc, “Custom channel groups can be applied to your reports retroactively” — the native channel can’t backfill history; a custom group can. It also covers the Perplexity gap and lets you split assistants into separate channels. Limits: standard properties get 2 custom groups (360: 5), up to 50 channels each, evaluated top-to-bottom, first match wins (Google).

One adjacent gotcha: sessions with incomplete UTM tagging can fall into Unassigned, because default channel rules key on source-and-medium combinations — Analytics Mania demonstrates a utm_campaign-only link doing exactly that. Medium

Why can’t GA4 show Google AI Overviews or AI Mode clicks?

Because AI Overview and AI Mode clicks arrive with a google.com referrer and land in google / organic — and a custom channel group can’t split an identical referrer. When we made that point in our Search Console guide, we cited practitioner analysis; Google’s own channel definitions now say it outright. Organic Search covers users who “arrive at your site/app via non-ad links in organic-search results, including Google’s AI Overviews and AI Mode” — and the AI Assistants definition explicitly excludes both.

So GA4’s AI Assistants channel measures the assistant side only. For the Google side, the closest thing to a lens is Search Console’s new Generative AI report — impressions only, no clicks, and still rolling out (our own property can’t see it yet); otherwise the data sits blended invisibly in the Web search type. That guide covers both. No regex fixes this; the referrer simply carries no AI signal to match on.

How much AI-assistant traffic should you expect?

Small — fractions of a percent to low single digits — but high-intent and growing fast. The honest anchors:

• Ahrefs’ own site (Patrick Stox, June 2025): AI search was 0.5% of traffic but drove 12.1% of signups — about 23x organic’s conversion rate, mostly from ChatGPT. That’s one company’s number, widely misquoted as a universal law; Stox himself notes AI-search users click links about 75% less and doubts the multiple holds at scale.
• Ahrefs’ 82,000-site study (June 2025): AI-referred visitors view fewer pages (4.0 vs 5.2), bounce more (67.8% vs 63.7%), but stay slightly longer (86s vs 78s).
• Similarweb: AI referral visits grew more than 3x between September 2024 and September 2025, and ChatGPT referrals convert at 7.1% in their panel — second only to paid search at 7.8%. After ChatGPT started surfacing more prominent clickable brand links on May 7, 2026, referrals across their desktop panel jumped 157.7% week-over-week (Similarweb).

Which AI-traffic stats should you not trust?

Any conversion figure that arrives without a primary source — starting with “AI visitors convert 4.4x better.” We’re not using it: retellings attribute it variously to Semrush and to Adobe, and we couldn’t find a primary source for either — contradictory attribution is disqualifying. More verified numbers live in our AI search statistics roundup.

On this site we watch the same referrer domains in PostHog rather than GA4 — the method isn’t GA4-specific, because the referrer is the signal, whatever tool catches it. And whichever tool you use, remember the great decoupling: being read by AI systems and being visited by humans are diverging metrics, and referrer tracking only sees the second.

Frequently asked questions

Sources

• Google Analytics release notes — New AI Assistant traffic measurement (May 13, 2026)
• Google Analytics Help — Default channel group definitions
• Google Analytics Help — Custom channel groups
• GA4 Optimizer — GA4’s AI Assistant channel
• Seer Interactive — Are AI sites like ChatGPT sending your website traffic?
• Swydo — How to track AI traffic in GA4
• MarTech — How GA4 records traffic from Perplexity Comet and ChatGPT Atlas
• Lawrence Hitches — utm_source=chatgpt explained
• DomainInvesting — OpenAI now using ChatGPT.com
• Ahrefs — AI search traffic and conversions (Patrick Stox)
• Ahrefs — AI traffic quality study (Louise Linehan)
• Similarweb — ChatGPT referral traffic triples
• Similarweb — Gen AI stats
• Analytics Mania — Unassigned in Google Analytics 4