The latest release of utag.js, version 4.52, introduces improvements to reliability, performance, and ease of use, particularly for customers with Single-Page Applications (SPAs) or performance-heavy tags.
What’s New In utag.js 4.52?
Version 4.52 of utag.js enhances Tealium iQ by improving usability, increasing predictability, and optimizing it for modern performance demands.
Historically, utag.view, utag.link, and utag.track calls have first been made available when utag.js has fully loaded on the page. That approach can cause problems for Single Page Applications (SPAs), which often need to fire events earlier than that on the initial app load (because they want to manually fire a ‘view’ event when the first screen loads in, not before).
Introducing Version 4.52’s Queuing System
This system ensures early tracking events are queued to be processed when utag.js loads. To take advantage of this feature, add the following snippet above your existing Tealium iQ implementation on your website:
(function(w){
if(w.utag)return;var u=w.utag={};u.e=[];
u.view=function(a,b,c){u.e.push({a:a,b:b,c:c,d:"view"})};
u.link=function(a,b,c){u.e.push({a:a,b:b,c:c,d:"link"})};
u.track=function(d,a,b,c){typeof d==="object"?
u.e.push({a:d.data,b:(d.cfg?d.cfg.cb:null),c:(d.cfg?d.cfg.uids:undefined),d:d.event}):
u.e.push({a:a,b:b,c:c,d:d});};
})(window);
Customers who don’t need this feature don’t need to make any changes – the above queuing snippet is not required for the utag 4.52 to run, just to take advantage of the new queue.
Important: This snippet only works with version 4.52 and later. Adding it with earlier versions will prevent utag.js from running, resulting in lost data.
Non-blocking Tags Can Improve INP Scores in Extreme Cases
Interaction to Next Paint (INP) measures how quickly a page responds to user interactions. It became a core Web Vitals metric in 2024, making it important for SEO. Most Tealium customers don’t have any issues with that metric, but for some pages with exceptionally resource-heavy tags, Tealium iQ may contribute to performance issues, since tags process before that ‘next paint’ by default.
If you can’t find ways to make your tags lighter and you’re having trouble with your INP score, version 4.52 introduces an option that might help: nonblocking_tags. By default, tags remain ‘blocking’ to ensure complete tracking, but this new setting supports asynchronous tag firing, improving INP scores by no longer running the tags before the ‘next paint’ after user interaction.
Tradeoff: While nonblocking tags improve performance, this setting also means tag execution no longer blocks navigation. Customers relying on that blocking behavior for critical tracking of such events should carefully evaluate this setting and test to make sure exit links are still captured as expected (introducing a navigation delay or similar if that makes sense for you).
If you want to know more, you can find a separate blog post, Interaction to Next Paint and Tealium iQ, that goes into more detail about that setting, the related research, and tradeoffs.
First-Party Session Counting Made Standard
Previously, Tealium’s session counting requests, often used as a billing metric, only fired for customers using a Tealium CDN to host their Tealium iQ files. That means that first-party and reverse-proxy customers have needed custom code to add those requests, creating unnecessary friction and upkeep for those customers.
Now, with Version 4.52, you can take advantage of standardized session counting logic using a new endpoint that works automatically out of the box, regardless of your setup.
- First-Party and Reverse-Proxy Customers: Remove any custom session logic to avoid duplicate counts.
- Self-Hosted Customers: Contact your Tealium Customer Success Manager to deactivate unused billing requests.
Performance Improvements and Predictability Fixes
A few other utag.js 4.52 updates are worth calling out:
- Reduced Cookie Reads: The new version minimizes reads of the utag_main cookie to convert between split and legacy cookie formats, and improves performance for pages with heavy cookies.
- Before Load Rules Consistency: Extensions scoped to “Before Load Rules” now execute reliably, even for tags called by UID (previously those extensions were skipped in that case). Legacy behavior can be retained with the suppress_before_load_rules_with_uids setting.
- More Reliable Event Attributes: Automatically generated tealium_* attributes (e.g., tealium_random) have previously not been overwritten if present on the incoming payload (if you set tealium_random to the string ‘this_is_not_random’, that silly value will be retained instead of being replaced with a random number). Now, except for tealium_event and tealium_visitor_id, such attributes are consistently set automatically. This won’t impact most customers but fixes downstream issues caused by reused objects in some advanced implementations.
Get Started With utag.js 4.52
utag.js Version 4.52 makes Tealium iQ easier to use, more predictable, and better suited for modern performance requirements. For customers using SPAs, those with resource-intensive tags and problematic Interaction to Next Paint scores, or first-party session setups, this release is worth prioritizing.
If you have questions or want to explore this further, see our Version 4.52 documentation, and reach out to your Tealium Customer Success Manager.
