Full Answer
Client-side = blockable, 30-40% loss. Server-side = unblockable, complete capture.
Client-side: JavaScript in browser (can be blocked by ad blockers, 30-40% loss). Server-side: code executes on server before page renders (unblockable, complete data). Pipeline readiness requires server-side to ensure 95%+ event capture.
Client-side = blockable, 30-40% loss. Server-side = unblockable, complete capture.