Core Web Vitals optimisation case study: UAL reduces container size & improves performance

The University of the Arts London (UAL) is the largest specialist Art and Design institution in Europe with over 18,000 undergraduate and postgraduate students. It comprises six specialist art and design colleges: Camberwell College of Arts, Central St Martins, Chelsea College of Arts, London College of Communication, London College of Fashion and Wimbledon College of Arts.

The UAL Digital Public Platforms team manages data from across 10+ sites and over 250,000 users a month.

The challenge

UAL had a Google Tag Manager (GTM) container filled with legacy tags and duplicate triggers and variables. This was resulting in a bloated container that had the potential to be slowing the site down and leading to a poor user experience.

The solution

We started with a full audit of the GTM container. The first step was to identify any duplicate, legacy or unreferenced tags, triggers and variables. We then reviewed the Custom HTML that existed within the container and found several areas where this could be optimised by condensing/consolidating similar tag types. We also suggested utilising Google Consent Mode to reduce the need for consent dependent triggers and updated the tag, triggers and variables to a structured and recommended naming convention. To prevent any ongoing issues we also audited the user permissions and made recommendations to reduce the number of users with publish permissions.

The results

Through a staggering total of 777 revisions in a single workspace, we accomplished two significant improvements. Firstly, we drastically decreased the container size, reducing it from 95% to 51%. Secondly, we reduced the execution time of the JavaScript from 3.5 seconds to an impressive 1.9 seconds. As a result, we achieved a noteworthy 26% reduction in the Total Blocking Time, a pivotal metric in Core Web Vitals.

What’s next?

UAL now has a condensed and organised GTM container that is no longer negatively impacting their Core Web Vitals. Following the actions from the user permission audit, they’re also able to more effectively manage changes and continue to maintain an optimised container.