Understanding the Client ID in Google Analytics 4: A Comprehensive Setup Guide

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Google Analytics 4 (GA4) being the latest version of Google’s web analytics platform, offers a powerful and flexible way to track user behavior on your website. One of the key features of GA4 is the Client ID, aka cid, a unique identifier that helps you track users across multiple sessions and devices. This guide will delve into the concept of Client ID in GA4, explaining its purpose, benefits, and how to set it up for accurate user tracking.

What is Client ID in GA4?

Client ID in GA4 is a unique identifier assigned to a user’s browser-device combination when they first visit your website. This ID persists across multiple sessions and devices, allowing you to track a user’s journey even if they switch devices or browsers. Unlike the User ID in GA4, the Client ID is automatically generated and doesn’t require any user action.

The Google Analytics (GA) Client ID is stored in a cookie named “__ga” (unless customised otherwise).

Both Universal Analytics and Google Analytics 4 (GA4) use client ID in the same way. However in the context of GA4 you may also see Client ID referred to using the synonym of “Device ID” from within the GA4 property settings > reporting identity configuration.

Why Do You Need a Client ID?

Client ID offers several benefits for website analytics:

Improved User Tracking:

By tracking users across sessions and devices, you gain a more holistic understanding of their behavior and journey. This allows you to analyze how users interact with your website over time, identify conversion paths, and personalize their experience.


Cross-Device Insights:

With the rise of multi-device browsing, Client ID becomes crucial for understanding how users move between devices. You can see how users research on one device and complete a purchase on another, providing valuable insights for optimizing your cross-device marketing strategies.


Enhanced Attribution Modeling:

Client ID enables more accurate attribution models, helping you determine which touchpoints contribute to conversions. This allows you to optimize your marketing campaigns and allocate resources more effectively.

How to Find Client ID in Google Analytics 4?

1. Locating the Client ID in Google Analytics 4 Interface:
To find the client ID within the Google Analytics 4 interface, follow these steps:
– Log in to your Google Analytics 4 account.
– Navigate to the Explore section.
– Click on User Explorer.

Within the User Explorer, you will discover the client ID listed for each individual user. By default, Client ID is only available in this Google Analytics 4 report. You can add a segment to it, but you cannot add other parameters to this report. To access the Client ID in other Google Analytics 4 reports, you must pass cid as a custom parameter.

2. Utilizing Google BigQuery:
In Google BigQuery, every event includes a field known as user_pseudo_id, containing the client ID.

3. Examining a _ga Cookie:
For a more technical approach, use the following steps:
1. Open your browser’s developer tools (usually accessible via F12 on Windows or by right-clicking the page and selecting “Inspect”). In this example, we’re using Google Chrome.
2. Go to the Application tab.
3. Navigate to Cookies and select your domain. Identify the _ga cookie, whose value might resemble something like this:
The last two numbers, separated by a dot, represent the client ID. In the provided example, the client ID is 292700308.1688836XXX


While client IDs in Google Analytics 4 (GA4) are crucial for tracking and understanding user interactions, there are certain challenges associated with them:


Cross-Device Tracking:
Client IDs are often used to associate user activity with a specific device. However, tracking users across multiple devices can be challenging. If a user switches devices or clears their cookies, a new client ID may be assigned, making it difficult to maintain a consistent user profile.


User Privacy Concerns:
Privacy regulations and user preferences regarding data privacy have become more stringent. The use of client IDs raises concerns about user privacy, especially when it comes to tracking users across different websites and platforms.


Cookie Deletion and Expiry:
Users can delete cookies or use browser settings to automatically clear them. When cookies are deleted, the association between the client ID and user history is lost. Additionally, cookies have an expiration period, so client IDs may change when cookies expire.


Limited Lifespan of Client IDs:
Client IDs are not permanent and may change under certain circumstances. For example, if a user hasn’t interacted with a website for an extended period, their client ID may change upon returning, leading to potential gaps in the tracking history.


Technical Challenges:
Implementing and maintaining accurate client ID tracking requires proper configuration and adherence to best practices. Technical challenges, such as misconfigurations or outdated tracking codes, can impact the reliability of client ID data.


Client ID is a powerful tool in GA4 that unlocks a wealth of user behavior insights. By understanding how to set up and utilize Client ID, you can gain a deeper understanding of your audience, optimize your website and marketing campaigns, and ultimately drive better business results.


  • Can I use the client ID to track conversions in Google Analytics 4?

    Yes, you can use Client ID to track conversions in GA4. By analyzing how users interact with your website before and after a conversion event, you can identify key touchpoints and optimize your conversion funnel.


  • What is the difference between User ID and client ID in GA4?
    User ID is a unique identifier that is based on user identification logic, while Client ID is automatically generated and assigned to a user’s browser-device combination. User ID provides more accurate user identification, but it requires users to log in, while Client ID offers broader tracking across devices and sessions without requiring any user action.

  • Is the GA client ID unique?
    Yes, the GA Client ID is unique to a specific browser-device combination. However, it’s important to note that the Client ID can change if a user clears their cookies or uses a different browser or device.

  • How is Client ID different from Session ID?
    Session ID is a temporary identifier assigned to a user’s browsing session on your website. It expires at the end of an internet browser session – which by default is 30 minutes of user inactivity, while Client ID persists across multiple sessions and devices.

About Author

Aarav is an accomplished professional specializing in digital analytics and data visualization. With a robust background in artificial intelligence projects, Aarav has consistently demonstrated a commitment to excellence. His expertise lies in harnessing data for insightful decision-making, and he excels in crafting compelling visualizations that effectively communicate complex information. Aarav's strategic approach and passion for innovation position him as a valuable asset at the forefront of digital analytics.

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