How to Track AI Referral Traffic in GA4 for a Law Firm Site

What you will build

A custom channel group is a rule-based category of traffic sources in Google Analytics 4. You define a channel, such as "AI assistants," by conditions on dimensions like Source and Medium. Google's help page says custom channel groups apply retroactively to your existing data, that you need the Editor role or higher, and that standard properties can have two custom groups besides the predefined one (360 properties can have more). The page also includes an example for AI assistants.

Step 1: Find your own AI sources first

1. Open the report

   In GA4, open Reports, then Acquisition, then Traffic acquisition.

2. Change the dimension

   Use the dimension dropdown to switch the primary dimension to Session source / medium.

3. Set a date range

   Pick at least the last 90 days so low-volume sources show up.

4. Scan the list

   Look for sources that belong to AI assistants and AI search tools. Write down the exact source strings you see. We have not verified a current list of source names, and they change, so use only what appears in your data.

Step 2: Create the channel group

1. Click Admin (the gear icon at the bottom left).
2. Under the property column, open Data display, then Channel groups.
3. Click Create new channel group and name it, for example "Default plus AI."
4. Click Add new channel and name it "AI assistants."
5. Add a condition group. Choose the dimension Source (or Session source), pick a match type such as "matches regex" or "contains," and enter the source strings you recorded in Step 1, separated with a pipe character if you use regex.
6. Drag the new channel above any broader channel (such as Referral) that would otherwise capture the same visits, because GA4 assigns a visit to the first channel whose rules match.
7. Save the group.

Menu labels in Google Analytics can change. If a step does not match what you see, follow the current instructions on Google's custom channel groups help page, listed in the sources below.

Step 3: Use it in reports

• In the Traffic acquisition report, change the channel group dimension to your new group to compare AI assistants with Organic Search, Direct and Referral.
• Add engagement and conversion events that matter to a law firm, such as phone call clicks and contact form submissions, if you have set them up.
• Compare month over month rather than reading a single month.

Step 4: Understand the undercount

A referral count only includes visits that carry referrer information that matches your rules. Visits can arrive without it, for example when someone copies a URL into a browser or an app opens a link in a way that strips the referrer. Visitors who see your name in an AI answer and then search for your firm will show up as Organic Search or Direct. So the channel is a floor, not a total.

Add a question to your intake form or call script: "How did you find us?" with an option for AI assistants such as ChatGPT, Gemini, Perplexity, Claude or Copilot. Combine it with the audit method in run an AI answer audit.

Step 5: Document and review

• Record which source strings your rule includes and when you added them.
• Review the Session source / medium list every quarter and add new sources you see.
• Annotate the dates you publish significant pages so you can connect changes in traffic to your work.

For the full measurement picture, see metrics that matter in AI search, and make sure the technical readiness checklist is complete so the traffic you want can arrive.