Manual Cross-Domain Tracking with gtag.js API: A Comprehensive Guide

Home Business Manual Cross-Domain Tracking with gtag.js API: A Comprehensive Guide
Cross-Domain Tracking with gtag

In the intricate landscape of web analytics, the seamless tracking of user behavior across various domains is pivotal. Google Analytics 4 (GA4) introduces a game-changing feature known as cross-domain measurement. This mechanism is engineered to ensure accurate attribution of user interactions as they traverse from one domain to another. In this guide, we delve into the nuances of cross-domain measurement, unraveling the vital role it plays in user tracking, the interplay of cookies, and the detailed steps to set it up manually.


Accurate Attribution with Cross-Domain Measurement
Cross-domain measurement is the cornerstone of cohesive user tracking across distinct online domains. It tackles the challenge of attributing activities accurately as users navigate from one domain to another. A notable feature is its ability to bypass the tracking of outbound clicks that lead to domains listed under cross-domain measurement. This ensures that these outbound links do not disrupt the seamless flow of tracking events.


Understanding Cookies and Cross-Domain Measurement

In the realm of user identification, cookies play a pivotal role. In the absence of cross-domain measurement, a user’s journey across different domains triggers the creation of new cookies with distinct IDs. Consequently, a single user visiting multiple root domains on the same device might be identified as separate entities, leading to skewed data insights.


With cross-domain measurement, the trajectory changes. As users navigate between domains using links or forms, cookies retain the same IDs. This seamless transition is achieved by passing cookie values from one domain to another via a specialized URL parameter (_gl). This transformation results in the identification of a single user and session, offering a unified perspective of their interaction.


Setting Up Cross-Domain Measurement via the Admin Interface

For those who are advanced users and prefer a hands-on approach, manual implementation of cross-domain tracking can be achieved through the gtag.js API. Here’s a code example illustrating the process:

// Retrieve client ID on the source domain
gtag('get', 'TAG_ID', 'client_id', (client_id) => {
// Store the client ID in a variable.
gtag('get', 'TAG_ID', 'session_id', (session_id) => {
// Store the session ID in a variable.

// Add client and session IDs to the link pointing to the destination domain
<a href=""></a>

// On the destination page, read the IDs from the URL and set them using the config command
gtag('config', 'TAG_ID', {
'client_id': getClientIdFromUrl(),
'session_id': getSessionIdFromUrl()

Validation of Cross-Domain Measurement

To ensure that cross-domain measurement functions seamlessly, rigorous testing is vital. The process involves:

  1. Navigating to a page containing links or forms pointing to domains configured for cross-domain measurement.
  2. Clicking on the link or submitting the form to transition to the destination domain.
  3. Verifying the successful loading of the page.
  4. Confirming the presence of the _gl linker parameter in the destination domain’s URL (e.g.,*abcde5*).
  5. If your website offers downloads, validating that downloads commence without hindrance.


Troubleshooting Cross-Domain Measurement

In cases where the _gl parameter is absent from the destination domain’s URL, ensure that the domain configured in the interface matches your website’s domain. Investigate the possibility of URL redirects or conflicts with other scripts that may disrupt proper cross-domain measurement.


Conclusion: Empowering Data Insights

Manual cross-domain measurement in Google Analytics 4 bestows a profound advantage in a data-driven world. By bridging the gap between domains, it empowers marketers and analysts to grasp the holistic journey of users. This intricate mechanism, fueled by cookies and precise tracking, is a cornerstone in harnessing actionable insights, ultimately shaping a comprehensive understanding of user behavior across the digital landscape.