Full Answer

The question matters because most stores operate with incomplete tracking data. GTM server-side is only cost-justified above approximately $250,000 per month in ad spend. At that level, recovering 5% more attribution accuracy is worth $12,500/month — easily clearing the $2,000+ monthly GTM overhead. At $20,000/month ad spend, the same 5% recovery is $1,000 — less than the maintenance cost alone.

Client-side tracking loses 30–40% of events to ad blockers, browser privacy restrictions, and consent rejection. That data loss compounds across every decision the store makes — from ad budget allocation to checkout design to attribution modelling. A store can't know its real conversion rate, its real cost per acquisition, or its real return on ad spend if the underlying events are incomplete.

Server-side tracking captures conversion events at the server before the browser has any chance to suppress them. The data survives ad blockers, Safari ITP cookie caps, and most consent restrictions for analytics processing. That reliability is what turns tracking from a reporting exercise into an operational advantage — the store with accurate data makes better decisions, and better decisions compound ([server-side tracking for WordPress](https://seresa.io/blog/server-side-tracking-wordpress/)).