Why it matters to a buyer
GTM makes tracking changes fast, a marketing team can add a new conversion tag without waiting on a developer release cycle, but that same convenience is also a common source of page speed problems, since tags accumulate over time and each one adds JavaScript that can compete for the browser's attention and hurt Interaction to Next Paint. A buyer should periodically audit what is actually loaded through GTM, since unused or duplicated tags are common on sites that have changed marketing tools or agencies over the years.
How it is measured or applied
GTM is installed once as a container snippet in the site's code, and after that, tags, triggers and variables are configured through GTM's own interface and published as new container versions without further code changes. Every change is tested in GTM's built-in preview mode before publishing to confirm tags fire correctly and on the intended pages. It is audited periodically by reviewing the full list of active tags for anything unused, duplicated, or loading on pages where it serves no purpose, and by checking the container's impact on page load performance directly in Chrome DevTools.
Sources
- About Google Tag Manager, Google Tag Manager Help
