In short. Key events from AI referrals measure important site actions grouped by assistant session source, with results shaped by event setup and counting method.

Definition: Key events from AI referrals are business-important website actions measured in visits attributed to an AI assistant. In Google Analytics 4 (GA4), this measurement combines events marked as key events with session traffic-source dimensions.

Key facts

As of 17 October 2026, Google's key event documentation requires an event measuring the relevant interaction to be created or identified, then marked as a key event.
The Traffic acquisition report includes Session source / medium, Key events and Session key event rate, allowing outcomes to be examined by session origin.
Google's counting method documentation distinguishes counting every occurrence from counting a key event once per session.
Google's attribution model documentation states that changing the reporting attribution model leaves Session source unaffected.

How is a site outcome configured?

An event records an interaction. Google's key event tutorial uses a confirmation-page view to create generate_lead, an event representing a lead. Its example settings include:

Event name: generate_lead
Mark as key event
Create without code
Trigger event name: page_view
URL: https://www.example.com/contact-us-submitted

This is Google's example configuration; the URL needs to match the site's confirmation page. The separate event confines the measured outcome to that page. Marking the underlying page_view event would treat all pageviews as key events.

Google's marking instructions place event management under Admin > Data display > Events. Existing events can be marked using the star icon. Marking applies from creation onward and leaves historical data unchanged, so the measurement period should begin after configuration.

How are outcomes compared by assistant source?

Google's Traffic acquisition documentation places the report under Reports > Acquisition > Traffic acquisition. Session source / medium identifies the source and medium associated with a session. For assistant-referral analysis, select that dimension and search the table for assistant source values present in the property's data.

Read Sessions alongside Key events and Session key event rate for the selected source. The rate measures sessions containing a key event divided by total sessions. Google's reporting guide also documents a key event selector, allowing the analysis to focus on the configured outcome.

The counting method determines how repeated actions contribute to counts. Once per event counts each occurrence; Once per session counts the key event once within that session. Record the chosen method when comparing reporting periods: changes apply only to future key events.

How does attribution affect interpretation?

Attribution assigns credit to interactions along a user's path to an outcome. Google's reporting attribution documentation distinguishes event-scoped dimensions such as Source from session-scoped dimensions such as Session source.

Changing the reporting attribution model affects reports using event-scoped traffic dimensions and can distribute fractional credit across interactions. Session-scoped dimensions remain unaffected. A report of outcomes grouped by assistant session source therefore answers a different question from a report distributing credit across the path. Preserve the dimension name alongside exported results so the measurement's scope remains explicit.

FAQ

How can I check that the outcome is recorded?

Google's reporting guide recommends the Realtime report's Key events by Event name card. You can also inspect DebugView, where a flag beside the event name identifies a key event.

Why is a newly marked event missing from standard reports?

Google's marking documentation allows up to 24 hours for a newly marked key event to appear in standard reports. Realtime updates a few minutes after an occurrence.

Can I measure sales revenue for the selected source?

Google's Traffic acquisition report includes Total revenue. For purchase data to populate this metric, you must send both value and currency with the purchase event; the metric also includes other documented revenue types and subtracts refunds.

Sources

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