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. Cookies can then be set server-side, which extends their lifetime in some browsers. Fewer third-party scripts in the browser can also help load time; that only holds up if you measure before and after. Server-side tagging relocates the data processing, it does not remove the need for consent: as long as data is stored on or read from the device, section 165 para. 3 TKG 2021 applies unchanged, and the operator is responsible for their own server container and for the onward transfer to analytics and advertising platforms. 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.