Server-Side Tagging (Server-Side Tracking)
Server-side tagging moves the processing of tracking data out of the user's browser and into your own server container, usually run on Google Cloud (Cloud Run or App Engine). Instead of many individual scripts in the browser, only one lightweight client call remains, while tags fire on the server and forward data to analytics or advertising platforms.
In practice
In practice, agencies set up a Google Tag Manager server container that is addressed through its own first-party subdomain, which keeps cookies valid for longer and makes them less likely to be blocked by browser tracking protection. Load time also improves, because fewer third-party scripts run in the browser. The effort is higher than with classic client-side tagging, since cloud infrastructure has to be operated, monitored and updated regularly – for smaller websites the switch often only pays off at higher traffic levels.