The CDN is designed to deliver these files to your website as quickly as possible. When the Universal Tag code snippet is executed by your webpage a request is made to the CDN, the file is downloaded into the page and the code is run. As soon as utag.js is loaded on your page it begins executing code to prepare to fire your tags.
Learn more about the order of operations to understand how the Universal Tag utag.js loads.
In addition to the dynamic data that your site populates into utag_data, the utag.js library automatically gathers other various data values from the page and combine them into one central data object to be made available to your tags and load rules. The following page elements are captured:
Query String Parameters
Meta Data Elements
The final data object are used to power your load rules and tags.
The code needed to load and run a vendor tag is also published to the CDN and stored in a tag configuration file numbered according to the UID of the tag, such as utag.1.js. An HTTP request is made to the CDN from your webpage to retrieve each tag configuration file.
Here is a simple example showing how one tag, Google Analytics, is loaded into the page:
utag.1.js (tags.tiqcdn.com) - the Tealium tag configuration file for Google Analytics
Improve page performance by bundling tags into utag.js to reduce the number of HTTP requests coming from your page.
Once all tag files are loaded and the DOM Ready event is reached, the tracking beacons are triggered. The vendor code runs the same as if it was outside of Tealium, so the resulting HTTP requests is easy to identify.
For example, Google Analytics is identified in the network request by the following two items: the analytics.js script and the collect image pixel. These same network requests occur even when Google Analytics is loaded via iQ Tag Management, as seen here: