AI assistant referrals

An AI referral is a visit that starts when someone follows a link in an AI assistant’s answer. GA4 records where each session came from as its session source. MeasureScale matches session sources against a list of AI assistants. It then sums the sessions for each assistant. The list is the AI referrer registry.

How to read the answer

• A good answer names each AI assistant, its sessions and its share of all your sessions.
• Treat the numbers as a floor. Some assistants send no referrer, so GA4 records their visits as direct traffic.
• The assistant list has not been checked against live GA4 data. Say so when you share the numbers.
• If GA4’s own AI channel counts more sessions than the list, the list is missing some sources.
• Visits from AI Overviews and AI Mode count as organic search. Ask your assistant about query shapes for a Search Console view.

What it answers

• How many sessions did each AI assistant send in the window?
• What share of all sessions came from AI assistants?
• Does GA4’s own channel grouping see more AI traffic than the registry names?

Inputs

MeasureScale reads two GA4 reports for the window. With no dates, the window is the last 28 settled days in the property’s time zone. A settled day is a day whose data Google has finished processing.

• The first report lists sessions and users by session source. MeasureScale matches assistants against it.
• The second report lists sessions and users by channel. It gives the total of all sessions.

Neither report has a filter. GA4 returns at most 10,000 rows for one report. The result says when GA4 had more rows than it returned. A rare source in the tail can then be missing.

How it works

• MeasureScale compares each GA4 session source with the AI referrer registry.
• A source that names a registered assistant counts toward that assistant. Subdomains count too.
• MeasureScale sums the sessions for each assistant and compares them with all sessions.
• It also reads GA4’s own AI Assistant channel as a check on the registry.

The registry

The registry recognizes these 13 assistants: ChatGPT, Perplexity, Microsoft Copilot, Google Gemini, Claude, DeepSeek, Grok, Meta AI, You.com, Phind, Mistral Le Chat, Poe and Qwen.

The registry has a version. Every result states it. The current version is 2026-10-08.1. The version changes when the list changes.

The list has not been checked against a live GA4 property that receives AI referrals. Every result says so. State this when you report the numbers.

Limits

• A hand-made list. People maintain the registry by hand. A new assistant or a new referrer host is missing until the list changes.
• Not yet verified. The list has not been checked against live GA4 data. The result says so.
• Short aliases. A short alias such as copilot, gemini or grok matches the whole source value only. A campaign that uses that word as its source also matches.
• Users do not add up. GA4 counts users separately for each source value. One person who arrives from two sources of one assistant counts as two users.
• Hidden referrers. Some assistants and apps send no referrer. GA4 then records the visit as direct traffic, and the registry cannot see it.
• AI features inside Google Search. Visits from AI Overviews and AI Mode count as organic search in GA4. This method does not find them. Query shapes offer a proxy on the Search Console side.
• No invented numbers. The registry holds no traffic data. Every number comes from the GA4 reports.