# AI Referral Traffic in GA4: AI Assistant Channel and Custom Regex > Track AI referral traffic in GA4: what the AI Assistant channel covers, a copyable custom channel regex, and how to check what slips through. Source: https://mentionx.ai/learn/ga4/ga4-ai-assistant-channel-regex Author: Dipuck Jones, founder of MentionX Updated: 4 November 2026 Level: Practitioner **GA4's default channel group now has an AI Assistant channel, but a custom channel group with a tight source regex still gives you a clearer, editable view of AI referral traffic, including past data.** Build it once, place it above Referral, and compare it with the default channel monthly. > **Key takeaways** > > - The default AI Assistant channel covers referrers on Google's own list, such as ChatGPT, Gemini, Deepseek, Copilot and Grok. > - Custom channel groups apply retroactively. Standard properties get 2 custom groups with up to 50 channels each. > - Google's example regex starts with `^.*ai`, which over-matches. Use the tighter regex below. > - Put your AI channel above Referral, and above Organic Search if you want it to win ties. > - AI traffic is undercounted either way, because apps often strip the referrer. *Checked 4 November 2026 (CET) against Google Analytics Help and Google developer documentation. GA4 menus and limits change, so confirm in your own property. "Our view" marks MentionX opinion. Ledgerline is a fictional company used for illustration.* ## How do you build the custom channel group? 1. Go to **Admin → Data display → Channel groups → Create new channel group**. 2. Name it, for example "Channels with AI split". GA4 copies the default channels in. 3. Click **Add new channel**, name it "AI assistants", set **Source** → **matches regex** and paste the regex below. 4. Use **Reorder** to move "AI assistants" above Referral (and above Organic Search). 5. Save. In **Traffic acquisition**, change the primary dimension to your new group. ## A tighter regex ``` ^(chatgpt\.com|chat\.openai\.com|openai\.com|perplexity\.ai|www\.perplexity\.ai|gemini\.google\.com|copilot\.microsoft\.com|claude\.ai|chat\.deepseek\.com|grok\.com|meta\.ai|chat\.mistral\.ai|you\.com|poe\.com)$ ``` If your property shows sources with paths or subdomains, use a looser end such as `(chatgpt|perplexity|claude|copilot|gemini|deepseek|grok)\.` and test it. Google's own example is: ``` ^.*ai|.*\.openai.*|.*chatgpt.*|.*gemini.*|.*gpt.*|.*copilot.*|.*perplexity.*|.*google.*bard.*|.*bard.*google.*|.*bard.*|.*.*gemini.*google.*$ ``` Because the first alternative is `^.*ai`, it matches any source containing "ai", including `mail.google.com` and many unrelated domains. Tighten it before you rely on it. ## How do you check what slips through? Run this monthly in a free-form exploration (lesson 9): rows = Session source, filter Session source matches regex `(gpt|ai|chat|copilot|gemini|claude|perplexity)` and compare with your channel. Add any genuine assistant you find to the regex and note the date. The [measurement guide to GA4 custom channel groups](https://mentionx.ai/learn/measurement/ga4-custom-channel-group-ai-referrals) goes deeper on regex testing, and [why AI referral traffic is undercounted](https://mentionx.ai/learn/measurement/ai-referral-traffic-undercounted) explains the Direct problem. > **Pro move:** add a second custom channel for "AI assistants (landing on /pricing or /demo)" using a Landing page condition alongside the source regex. It shows whether AI visitors arrive ready to buy, which raw sessions hide. *Our view:* the default AI Assistant channel is the right number for trend lines because Google maintains it. Your custom group is the right one for diagnosis. Report both, labelled. ## Example: Ledgerline Ledgerline (fictional) built the group and saw `chatgpt.com`, `perplexity.ai` and `copilot.microsoft.com` as separate rows, with most AI visits landing on comparison pages. That pointed its content team at comparison content rather than the blog. For assistant-specific tracking, see [measuring brand visibility in Claude](https://mentionx.ai/learn/claude/measure-brand-visibility-claude) and [Tracking ChatGPT referral traffic and mentions](https://mentionx.ai/learn/chatgpt/track-chatgpt-referral-traffic-mentions). Next: [Customising standard reports and the library](https://mentionx.ai/learn/ga4/ga4-reports-library-customise). Or return to the [GA4 for Marketers track](https://mentionx.ai/learn/ga4/ga4-for-marketers). ## Common questions **Do I still need a custom AI channel if GA4 has AI Assistant?** It is still useful. The default list isn't published in full, and a custom group lets you split assistants individually, apply your own definition and relabel past data. **Is Google's example regex safe to use?** Use it with care. It starts with ^.*ai, which matches any source containing "ai", such as mail domains. A tighter list of known domains is safer. **Can GA4 see AI Overviews traffic separately?** No. Google classes AI Overviews and AI Mode as Organic Search, and the referrer is google. Search Console is the place to look. ## Sources - Google Analytics Help, [Custom channel groups](https://support.google.com/analytics/answer/13051316) - Google Analytics Help, [Default channel group](https://support.google.com/analytics/answer/9756891) - All accessed 4 Nov 2026. ## Frequently asked questions ### Do I still need a custom AI channel if GA4 has AI Assistant? It is still useful. The default list isn't published in full, and a custom group lets you split assistants individually, apply your own definition and relabel past data. ### Is Google's example regex safe to use? Use it with care. It starts with ^.*ai, which matches any source containing "ai", such as mail domains. A tighter list of known domains is safer. ### Can GA4 see AI Overviews traffic separately? No. Google classes AI Overviews and AI Mode as Organic Search, and the referrer is google. Search Console is the place to look. --- Written and reviewed by Dipuck Jones for MentionX Learn. The HTML version of this page: https://mentionx.ai/learn/ga4/ga4-ai-assistant-channel-regex