Google Tag Manager
A free tag management system that lets you deploy and update marketing and analytics tags through a web interface instead of editing site code directly. Tags fire based on triggers and can read values from the data layer, giving marketers control over tracking without a developer for every change.
Why It Matters
GTM decouples measurement from release cycles, so you can add conversion tags, remarketing pixels, and analytics events in minutes. It also centralizes tag governance, reducing the duplicate and orphaned scripts that slow pages and corrupt data.
Common Mistake
Publishing a container without using Preview mode first, then discovering tags fire twice or never. Always test triggers in Preview and confirm events land in GA4 before publishing to the live site.