We are currently experiencing an issue with the use of Tag Manager and A/B Testing.
Here’s the situation:
The page is accessible at: www.ourdomain.abc
Our tracker is only accessible at: tracker.ourdomain.abc
On the page, we exclusively load the container_abc123.js from Tag Manager. During the page view, a Matomo configuration is loaded, which makes the following important settings:
Domains: *.outdomain.abc
Cookie Domain: .ourdomain.abc
Bundle Tracker: True
Register as Default Tracker: True
We have integrated the following additional code on a page:
<script type="text/javascript">
var _paq = _paq || [];
_paq.push(['AbTesting::create', {
name: '125',
percentage: 100,
includedTargets: [{"attribute":"url","inverted":"0","type":"equals_simple","value":"https:\/\/www.ourdomain.abc\/test-a.html"}],
excludedTargets: [],
startDateTime: '2023/07/14 00:00:00 UTC',
endDateTime: '2023/09/14 23:59:59 UTC',
variations: [
{
name: 'original',
activate: function (event) {
// usually nothing needs to be done here
}
},
{
name: 'SiteB',
activate: function(event) {
event.redirect('https://www.ourdomain.abc/test-b.html');
}
}
]
}]);
</script>
Now, the following occurs:
If the page is visited and the A/B test chooses the original, a tracking request is generated (e.g., https://tracker.ourdomain.abc/matomo.php?e_c=abtesting&e_a=125&e_n=original&…). Here, the following cookie is created, which contains a new VisitorID:
_pk_id.17.xyz // Domain: www.ourdomain.com // SameSite: Lax
(Note the difference in Tracking URL and Cookie Domain.)
Subsequently, the Tag Manager Tags generate additional tracking requests. These Requests naturally ignores the cookie from www.ourdomain.com and therefore create a new cookie with a new VisitorID:
_pk_id.17.xyz // Domain: .ourdomain.com // SameSite: Lax
This behavior now leads to a “empty visitor” being recorded with 0 actions. This visitor only has the information that they are participating in an A/B test. The second visitor (the actual visitor) generated by the Tag Manager now has all the other information of the real visitor but is not counted in the A/B test statistics.
If we add the cookie information to the A/B test snippet, we achieve the desired behavior:
_paq.push(["setDomains", [".ourdomain.abc"]]);
_paq.push(['setCookieDomain', '.ourdomain.abc']);
Loading the matomo.js synchronously beforehand and explicitly configuring the JavaScript tracker is not an option for us. Furthermore, we followed the recommendation of the A/B Testing Plugin and did not add the code as Custom HTML in the TM Container.
We assumed the following:
- DOM Ready or Pageview event initializes the tracker with the TM option: “Initialize Only. Don’t track anything.”
- Due to “Register as Default Tracker,” it is available to all plugins or further tracking requests.
- Tracking events from plugins wait until the tracker is initialized and then use the full configuration.
Are we doing something wrong? Or is the implementation not intended in this way?
