[UA] User-ID limits [Legacy]

User-ID values are not assigned by Analytics

Analytics cannot generate, assign, or manage the unique IDs that are assigned as User IDs. In a typical scenario, IDs can be generated through your authentication system, passed to an account when a user signs-in, and then sent to Analytics. (You can, however, set up User-ID in different ways, and are not limited to associating it with account sign-ins.)

Data collection begins after implementation

User-ID can only collect data after you’ve implemented the feature. Implementation includes the generating unique IDs, assigning IDs to returning users, and sending IDs and all related engagement data to Analytics. Any data in your Analytics account collected and recorded prior to implementation cannot be reprocessed and associated with a User ID.

Availability of data from product integrations

Data from the following product integrations is available in User-ID views:

• Google Ads
• Search Ads 360 

Data from the following product integrations is not available in User-ID views:

• Display & Video 360
• Campaign Manager 360
• Google Ad Manager 

Feature limitations

The following Analytics features are not compatible with User-ID:

• Real-Time reports
• Demographics and Interests reports
• Enhanced data freshness

Universal Analytics guidelines and policies apply

The User-ID feature is built for use with the Universal Analytics technologies. All implementations must comply with the Analytics Measurement Protocol / SDK / User ID Policy. The Universal Analytics usage guidelines, and security & privacy principles also apply.

Opting-out of Analytics

Website users that don’t want their data reported by Analytics can install the Analytics opt-out browser add-on, which instructs Analytics JavaScript to prohibit sending data to Analytics. This can affect data collection of Analytics technologies, including Universal Analytics and the User ID.

User-ID data can't be merged

The User-ID feature can be implemented on any Universal Analytics property, but data collected in one property cannot be shared or mixed with data in another property. Analytics 360 users can use Roll-Up Reporting in conjunction with User-ID to aggregate data from multiple properties into a single property.

Remarketing audiences based on User-ID data are ineligible for some destinations

If you create Remarketing audiences from data in User-ID views, those audiences are not eligible to activate in Google Ads, Display & Video 360, or Google Ad Manager.

Related resources

• Analytics opt-out browser add-on
• Security & privacy principles in Universal Analytics
• Universal Analytics usage guidelines
• Benefits of using the User-ID feature
• Overview of the User-ID feature

• Measurement Protocol / SDK / User-ID Policy