GA4’s default client-side collection loses events to the same browser pressures as every pixel. Moving collection server-side (sGTM or a managed pipeline) restores completeness and puts consent enforcement in one place.
Setup modes
Client-only is the default: the browser sends everything, and the browser is where events get lost. Hybrid is the common pattern: client capture, server delivery. Server-first collects and delivers away from the browser entirely.
What you gain and what it costs
The practical wins: fewer lost sessions, first-party cookie lifetimes, one consent gate instead of per-tag consent logic.
The practical costs: infrastructure to run, and a handful of GA4-specific quirks (quota behavior, debug tooling differences) worth knowing before migration.
The export is the point
The BigQuery export then becomes your activation source: GA4 data feeding audiences and conversions back to ad platforms through the warehouse connection. Collection quality upstream decides what that export is worth downstream.
Setup steps and FAQs are on the GA4 server-side connection page.