In addition to the dynamic data that your site will populate into utag_data, the utag.js library will automatically gather 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 will be captured:
Query String Parameters
Meta Data Elements
The final data object will then be used to power your load rules and tags.
Load Rules are precise conditions that determine when to load a tag. Generally made up of one or more conditions, a load rule has to be satisfied in order to load the tag to which it is applied. The full list of variables from the data object will be used to evaluate the load rules and determine which tags will load on the page.
Here is a simple example showing how one tag, Google Analytics, would be loaded into the page:
utag.1.js (tags.tiqcdn.com) - the Tealium tag configuration file for Google Analytics
You can 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 will be triggered. The vendor code runs just as it would outside of Tealium, so the resulting HTTP requests will be easy to identify.
For example, Google Analytics is identified in the network requests by two items: the analytics.js script and the collect image pixel. These same network requests will occur even when Google Analytics is loaded via iQ Tag Management, as seen here: