Google Analytics

GA4 Cross Platform Tracking + Measurement ID: How It Fits Together

Setting up, Testing, and Navigating Cross Platform Tracking and Measurement ID

Main Image Courtesy of Co-op Web Builder

GA4 is built on a new architecture that gives it the ability to collect more data and provide you with more insights. It’s important to analyze and visualize the complete experience of your app or website, which can be done with the help of various tracking and measurement features in the newest version of Google Analytics. 

Comparing Universal Analytics 

GA4 is built on top of events and parameters, which makes it different from Universal Analytics. The user's journey is not linear, as they may use different devices and touchpoints throughout the process of converting. For instance, the first interaction a user has with your business may happen on their smartphone, while the purchase could happen on their desktop.

Through its new measurement model, GA4 can now track the data collected from both apps and web in one place, giving you a more accurate view of the user's journey. Furthermore, it can perform more granular analysis by having separate streams for iOS, Android, and the web.

What is Cross-Domain Tracking in GA4?

One of your company's websites has two domains. For example, if you have a visitor who has landed on your first website, and GA4 stores a cookie in their browser, they will be redirected to your second site after clicking on a link. This is a part of their user journey.

Although Google Analytics will automatically activate GA4 on this website, the value of the cookie on this domain is different from that of the first one. As a result, even though the individual users are the same, the actions taken on this site will be treated as separate entities.

Cross-domain tracking is a type of security that allows you to track the activities of your users on different websites. For instance, if a visitor lands on your first website, then a cookie is saved. When they go to the second website, the second one will also keep track of the cookie data. This means that the same cookie will be used on both sites.

Google Analytics uses a unique ID for each user and session. This allows it to provide more precise reports by identifying the users and their activities.

Purpose of Cross-Domain Tracking 

Setting up cross-domain tracking is an important part of your Analytics property's configuration if you have multiple websites.

Unfortunately, Google Analytics doesn't support automatic tracking of users who move between multiple websites. This is because the platform stores first-party cookies on your users. When a user visits your site, this cookie stores their unique ID.

Although Google Analytics can track a user's visit to one website from another, it can't follow them across multiple sites. This means that if a user moves to another website, it will record them as two distinct users.

This issue can seriously affect your data collection, as it will allow Google Analytics to track the same user across multiple websites. This means that it will appear as if you have several users instead of one. It can also cause issues with traffic acquisition reports, as if a user who visits one site gets recorded as a "self-referral."

One of the most effective ways to prevent this issue is by implementing cross-site tracking. This will allow Google Analytics and other third-party platforms to track the users' journey across multiple websites. In the next section, we'll talk about how to implement this.

How to Set Up Cross-Domain Tracking in GA4

Take a look at how to set up cross-domain tracking in GA4 in order to get started:

  • In the GA4 property, click on the "Admin" button. Then, go to "Data streams" and "More tagging settings." You will then be able to configure your domains.
  • To configure cross-domain tracking, go to the "Add condition" button after you clicked the small pencil icon and enter all the domains that you want to track.
  • Finally, make sure to click the "Save" button so that you don't lose any important information. The process is now complete, you're done setting up cross-domain tracking!

Cross-Device Tracking Methods in GA4

Take a look at the following methods that will help you to better track and understand user behavior. 

User ID

One of the most important identity spaces that you can use to track the behavior of your users is the User-ID. This allows you to keep track of their activities across various platforms and devices.

Through the use of Google Analytics, you can easily stitch your own unique identifiers into a single user's account, which will allow you to track their activities across multiple platforms.

Unlike other identity methods, this method is very powerful and can be implemented in a custom way. However, it's only available on websites where people enter their data, such as their names, phone numbers, and email. A key is generated for this identity space.

You can create a string of characters for each user who logs into your website using the email address that they provided. This will allow you to collect a unique ID that will be used to track their activities across various applications and platforms. However, you cannot collect personal information from this ID.

Google Signals

When a user fails to log in to a website and doesn't provide any identification data, Google Signals may be helpful. When a user signs in with Google, they can be improved upon in tracking their device's cross-device activity. Also, through their Ads personalization feature, they can be used to identify their identity across different devices.

This method doesn't require a tracking code, and it's very easy to implement. However, it's important to note that not everyone who visits your website is a Google user, so this method should be considered a complement to other identifiers. Image Courtesy of the Cookie Script.

Device-ID Tracking

Device ID tracking is the standard method of identifying a user. It only recognizes the devices that are connected to the network. This method is based on a browser's _ga cookie and the unique installation of an app.

When a user visits your website from their mobile device, they will receive different cookies depending on their device. This means that you can't correlate their visit to your site with their purchases on a desktop.

Although device-tracking can help you identify a user, it's not always accurate to track their journey. Other methods need to be supported in order to accurately identify them.


This identity space can be used by people who don't want to give away their cookies or other identifiers. If your app or website displays a consent banner, you might lose the users who don't want to be tracked.

In order to fill in the gap, Analytics uses information collected from other users who don't allow the tracking of their cookies. This data is then used to create a representation of the behavior of those who do allow the tracking.

Testing Your Cross-Domain Tracking 

To configure cross-domain tracking correctly, you should use your debug view. You can access it through the "Configure" button, and it will generate a real-time report that you can use to test. To verify that your system is working properly, open up the debug view, and interact with your domains from your gadget.

When you click from one site to another, GA4 will trigger an outbound link click, which will be displayed just as a "click" in your debug view. This happens if you click on an embedded link that takes you to another site.

Setting up cross-domain tracking will let you know that it's working properly. One of the most important things you can do is to confirm that the embedded link will no longer show as an outbound click when you navigate from one site to another. Doing so will allow you to test the system's configuration.

You can also check the URL of the site you're visiting as you navigate from one destination to another to confirm the cross-domain configuration that you have set up. After you've created cross-domain monitoring, go to one of the sites you're visiting and click on the embedded link. If you notice a query parameter, it means that the system is working properly.

Measurement ID

Prior to starting to track your performance in Google Tag Manager or Google Analytics, you must first enter your measurement ID

This is similar to the tracking ID used previously in Universal Analytics. Image Courtesy of Google Help. 

Comparing Measurement ID and Tracking ID

There are some major differences between the GA4 and Universal Analytics properties. One of these is the change in the measurement ID. In Universal Analytics, you had a tracking ID, but now you have a measurement ID.

You must use your tracking ID to access the data collected by Universal Analytics. This string, which looks like UA-000000-4, must be inserted into the code of your website's tracking system to allow Analytics to know which property or account it should send the information to.

If you're using Google Analytics 4 on a site, then you'll need to use the measurement ID to track the data collected by the system. This ID will be formatted as G-XXXXXXX and will send the information to the GA4 property.

Property ID vs. Measurement ID

In GA4, you will have one or more measurement IDs and a property ID. It's important to keep in mind that these two IDs should not be confused.

Your property ID is unique and is associated with your account with Google Analytics. It doesn't identify the data streams of the platform. The measurement ID on the other hand is a unique piece of information that denotes the source of data that you wish to collect from a particular stream, typically a mobile app or website.

Multiple Data Streams/Measurement IDs

In GA4, you can have numerous data streams feeding into one property. Each of them has its own unique ID, but the property's ID will remain the same across all of them.

You can create a data stream for each of your properties in GA4, including your website and mobile app. This will allow you to track both of them. The measurement ID of each data stream will be unique, allowing you to differentiate between the information that you gather from your app and from your website. But, the two data streams also have the same ID, which will let you know if you have a Google Analytics account.

Complete the Easy Cross-Domain Tracking Setup in GA4 Today

In GA4, setting up cross-domain tracking is made as easy as can be. You can easily enter the websites that you want to track and it will allow you to track the users who move throughout your sites. Cross-domain tracking is not the same as subdomain tracking, so you don't have to set up a separate program as it will automatically track users between your app and website. With the new and improved measurement ID, your tracking options are endless!

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