This article will describe how to use the data-domain HTML tag for an existing Ascend snippet in order to successfully track users across subdomains. For any Ascend experiments that navigate across multiple subdomains, this This guide is relevant for versions of the product past 8/30/2017.

The Data-domain HTML attribute

The data-domain tag in an Ascend snippet is used to describe to Ascend what the parent, or 'Apex,' domain should be for Ascend user tracking. In more technical terms, when a data-domain is set, the user tracking cookie Ascend uses for attribution and candidate rendering will be set at the domain passed into the attribute.

For example, lets say that your website sits at, but your shopping cart uses the subdomain of In this example, you would need to let Ascend know that your Apex domain is ''

Let's take a look at the Ascend snippet to see how to set this up correctly - this is how your snippet might look when logged in to the product and on the experiments dashboard page:


The snippet in this example is :

<script src="//"></script>

To set the Apex domain to '', this is how you should augment your script:

<script data-domain="" src="//"></script>

Confirming that the Apex/Parent domain has been properly set

It is fairly simple to check that the setup on your site is correct. When using a Chrome browser, go through the following steps:

1) Navigate to the web page that your Ascend snippet is placed.

2) Open the Chrome developer console.

3) Navigation to the 'Application' tab.

4) Under the Application tab, navigate to the dropdown for 'Cookies.'

5) Search for the following cookies - each should have the 'domain' set to the domain you have entered for your Apex or parent domain:


As always, please reach out to your solutions engineering and customer success teams if you are having any issues with this implementation.

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