How I Built a GTM Debugger Chrome Extension (And What I Learned the Hard Way)

Every GTM developer has been there. You fire a tag, open the preview mode, and... nothing. The tag didn't fire. Or maybe it did fire, but with the wrong dataLayer values. You refresh. You check the trigger. You stare at the screen. You start questioning your life choices. I've been doing Google Tag Manager implementations professionally for years, and this frustration never went away. GTM's built-in debugger is powerful, but it's slow to load, tied to a separate window, and shows you a lot of noise when you just want to check one thing : did my dataLayer event push correctly? So I built Tag Master — a Chrome extension for GTM and GA4 debugging. Here's how it went, what I built, and what I wish I'd known before starting. The Problem I Was Actually Solving Before writing a single line of code, I spent time articulating exactly what the pain was: dataLayer inspection is painful — you either console.log(dataLayer) manually or dig through GTM Preview's cluttered UI Network request decoding