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Last Updated: May 24, 2022

This article is the 4th in the series of cross domain tracking.

The first article was: Google & Universal Analytics Cookies where I explained cookies in great detail. Knowledge of cookies helps a lot in understanding and troubleshooting cross domain tracking issues.

The second article was: Cross domain tracking in Google Analytics where I explained implementing cross domain tracking when the websites (source domain and destination domains) are using ga.js JavaScript library (aka the old Google Analytics).

The third article was: Cross domain tracking in Universal Analytics where I explained implementing cross domain tracking when the websites are using the analytics.js JavaScript library (aka Universal Analytics).

In the present article, I am going to explain implementing cross domain tracking via GTM.

I won’t be able to explain the very basics of cross domain tracking here and assume that you understand linker parameter,  allowLinker, ‘auto’ and other cross domain tracking jargon (explained in great detail in the articles above).

Like any other GTM implementation, basic understanding of corresponding standard GA implementation is expected and that is why I never introduce any concept/topic via GTM.

There are two methods you can use to set up Cross Domain Tracking with Google Tag Manager:

1) Decorate Link and Decorate Form tags (esp. used in case of ga.js)
2) Auto Link Domains (analytics.js only).

I am going to explain implementing cross domain tracking in GTM via ‘Auto Link Domains’.

I won’t cover cross domain tracking via ‘decorate link’ and ‘decorate form’ tags as they are required only when you are using old Google Analytics and if you are still using old Google Analytics then I would strongly urge you to upgrade to Universal Analytics instead of trying to implement cross domain tracking for the old GA.

For the purpose of explaining the cross domain tracking concept in GTM, let us suppose we want to implement cross domain tracking between two primary domains: abc.com (the source domain) and xyz.com (the destination domain) via ‘Auto Link Domains’.

Both of these domains contain different Universal Analytics Tracking code and are treated as completely different websites.

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Google Analytics configuration for abc.com

Step-1: Create a copy of the main GA view of abc.com by going to Admin > View > View Settings > Copy View:

We are creating a copy here in order to maintain one unfiltered view.

Step-2: Name the new view ‘ABC Cross Domain Tracking View’

Step-3: Apply following custom advanced filter to the new view:

This view adds host name (domain name) to the request URI.

Step-4: Go to Admin > Property > Tracking Info > Referral exclusion list in ‘ABC Cross Domain Tracking View’ and add ‘abc.com’ in the ‘referral exclusion’ list:

Google Tag Manager Configuration for abc.com

Step-1: Login to the GTM account of abc.com website and edit the tag you used to deploy Universal Analytics tracking code on your website:

Step-2: Find the field ‘More Settings’ > ‘Fields to Set’ and set ‘allowLinker’ to ‘true’ and ‘cookieDomain’ to ‘auto’

Note: I am using Google Tag Manager V2 (the latest version of GTM).

Step-3: Scroll down further to find Cross Domain Tracking > Auto Link Domains (under ‘More Settings) and enter ‘xyz.com:

If you want to implement cross domain tracking across multiple domains then enter comma separated list of domains in the ‘AutoLink Domains’ text box:

If your source domain link to destination domain via form and you want to share cookie information on form submission then set ‘Decorate Forms’ setting to ‘True’ as shown below:

Step-4: Your Universal Analytics tag configuration should look like the one below:

Step-5: Click on the ‘Save Tag’ button.

Step-6: Create a new version of the container, test it and then publish it.

Google Analytics configuration for xyz.com

GA configuration for xyz.com is similar to abc.com configuration:

Step-1: Create a copy of the main GA view of xyz.com

Step-2: Name the new view ‘XYZ Cross Domain Tracking View’

Step-3: Apply the custom advanced filter to the new view which append domain name to the request URI.

Step-4: Add ‘xyz.com’ in the ‘referral exclusion’ list:

Google Tag Manager Configuration for xyz.com

GTM configuration for xyz.com is similar to the GTM configuration for abc.com. Make sure that your Universal Analytics tag configuration look like the one below:

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Implementing tracking across the Primary domain and its sub-domain(s)

By default, Universal Analytics can track traffic across all sub-domains of your website. However, you still need to configure your GA and GTM to make sure that you can distinguish the traffic from different domains in analytics reports.

Follow the steps below to track across the primary domain (say abc.com) and its sub-domain (say music.abc.com):

Google Tag Manager Configuration for abc.com and music.abc.com

Step-1: Use the GTM container code of abc.com on all of the pages of music.abc.com. So you will have one GTM account for managing tags on both the primary domain and its sub-domain(s).

Step-2: Edit the tag you used to deploy Universal Analytics tracking code on the websites abc.com and music.abc.com:

Step-3: Find the field ‘More Settings’ > ‘Fields to Set’ and set ‘cookieDomain’ to ‘auto’:

Here we are using ‘auto’ configuration parameter while creating a tracking object so that Google Analytics automatically set its cookie to the highest level domain possible.

Note: Without using the ‘auto’ configuration parameter, you cross domain tracking will not work whether you implement cross-domain tracking between primary domain and its sub-domains or between two or more different primary domains.

Google Analytics Configuration for abc.com

Step-1: Create a copy of the main GA view of abc.com

Step-2: Name the new view ‘ABC Cross Domain Tracking View’

Step-3: Apply the custom advanced filter to the new view which append domain name to the request URI.

Step-4: Add ‘www.abc.com’ in the ‘referral exclusion’ list.

Google Analytics Configuration for music.abc.com

Step-1: Create a copy of the main GA view of music.abc.com

Step-2: Name the new view ‘ABC Music Cross Domain Tracking View’

Step-3: Apply the custom advanced filter to the new view which append domain name to the request URI.

Step-4: Add ‘music.abc.com’ in the ‘referral exclusion’ list.

Other articles on cross-domain tracking

• Cross Domain Tracking in Google Analytics – Complete Guide
• How to check cross-domain tracking in Google Analytics
• Google Analytics Subdomain Tracking Tutorial
• Cross Domain Tracking in GA4 (Google Analytics 4) Setup Guide
• Setting up Sales Funnel across websites in Google Analytics
• Google Analytics cookies: _ga cookie, _utmb, _gat – Tutorial