• Data Source: Google Analytics 4 (GA4)
  • Type: Text (Unique Identifier)
  • Definition: Client ID in Google Analytics 4 is a unique identifier assigned to each browser on a user’s device that interacts with your website. It is used to track and analyze individual user behavior across sessions. The Client ID is typically a randomly generated string stored in a browser cookie.


The Client ID is fundamental to understanding user interactions over time, enabling GA4 to distinguish between new and returning users and to compile their activities into coherent sessions. By tracking how individual users engage with your site across multiple visits, Client ID helps in creating a detailed picture of user behavior, preferences, and engagement patterns.

Use Cases

  1. User Behavior Tracking: Utilize Client ID to track individual user interactions over time, gaining insights into user journeys, engagement patterns, and preferences.
  2. Session Analysis: Analyze sessions associated with unique Client IDs to understand user engagement depth, session duration, and the frequency of visits.
  3. New vs. Returning User Analysis: Leverage Client ID data to differentiate between new and returning users, analyzing behavior differences and engagement trends among these groups.
  4. Cross-Device Tracking: In conjunction with User ID, if implemented, use Client ID to understand user interactions across devices, provided users authenticate on each device.
  5. Personalization and Targeting: Inform personalization strategies and targeted marketing by understanding individual user behavior and preferences as indicated by their Client ID-associated activities.


The effectiveness of Client ID-based tracking can be influenced by factors like cookie expiration, users clearing cookies, or using incognito modes, which might result in the generation of new Client IDs and potentially skew user tracking data.

Upgrade your reporting today!

Try our free demos and see the difference. No payment required.