What happens if an AI assistant domain is added to GA4's unwanted referrals?

Definition: In Google Analytics 4 (GA4), unwanted referrals are domains whose referrer information is suppressed as a traffic source. As of 17 October 2026, adding an AI assistant domain applies this rule to matching events through the ignore_referrer parameter.

Key facts

• Google's unwanted referrals documentation says matching events receive ignore_referrer=true; the conditions apply across pages carrying the Google tag.
• Google's campaign processing documentation treats an ignored referring source as Direct, while an earlier referral can retain attribution.
• Google's configuration reference provides both global and individual stream settings for ignore_referrer.

What happens to source attribution?

Attribution assigns credit to traffic sources. Google's campaigns documentation says the document referrer can populate dimensions when other campaign or traffic-source fields are absent. Campaign parameters in the landing URL provide another input: custom campaign values map to report dimensions. An excluded assistant referrer therefore does not force every tagged visit into Direct.

The same documentation states that a direct visit following a referral does not override the existing referrer. Google's unwanted referrals example describes a visit from Domain B before exclusion and a direct return attributed to Domain B through last-non-direct-click attribution. Excluded domains can remain visible for returning users.

Where is the unwanted referrals setting?

Google's configuration instructions place the setting at Admin > Data collection and modification > Data streams > Web, then the selected stream, Configure tag settings > Settings > Show all > List unwanted referrals.

Each condition specifies a match type and domain identifier.

Can ignore_referrer be set in code?

Google's configuration reference supplies this individual stream example, where STREAM_ID represents the stream identifier:

gtag('config', 'STREAM_ID', {
  'ignore_referrer': true
});

Google's unwanted referrals guidance warns against applying the parameter on every page because valuable traffic-source information can be lost.

How can the reported source be checked?

Google's Traffic acquisition report documentation locates the report under Reports > Acquisition > Traffic acquisition. Its Session source / medium dimension describes the source and medium associated with a new session. The table's search field selects a traffic source. This report includes acquisition for both new and returning users.

Related terms

• AI referral traffic
• GA4 traffic acquisition
• UTM parameters
• HTTP Referer header

FAQ

Does explicitly setting ignore_referrer to false restore referral attribution?

Google's help page states that setting any value, including false, causes the referrer to be ignored for attribution.

How can you hide a source in one report?

Google's Traffic acquisition instructions describe a report filter: select Add filter, change Include to Exclude, choose Session source, select its values, then select OK and Apply.

Sources

1. Google Analytics Help, "Identify unwanted referrals", undated
2. Google Analytics Help, "Campaigns and traffic sources", undated
3. Google for Developers, "Configuration", 5 October 2026
4. Google Analytics Help, "[GA4] Traffic acquisition report", undated

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