# AI assistant referrals

> How MeasureScale counts GA4 sessions that AI assistants such as ChatGPT, Perplexity and Claude send to your site.

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](/methodology/search-shape/) offer a proxy on the Search Console side.
- **No invented numbers.** The registry holds no traffic data. Every number comes from the GA4 reports.