Tag Manager is not analytics, and confusing them costs you

Google Tag Manager collects nothing. It is a container that loads other things — analytics tags, ad conversion tags, third-party scripts — according to rules.

This distinction sounds pedantic and produces a genuinely common failure: a site with GTM installed, nothing configured inside it, and everyone assuming measurement is handled.

The half-finished install

It looks like this: the container snippet is in the template, it loads correctly, the GTM preview mode connects. And there is no GA4 configuration tag, or there is one with no measurement ID, or it is paused, or it was never published — the change sits in a workspace nobody submitted.

That last one is the cruellest. Everything looks correct in the interface; the live container has none of it.

Why nobody notices

The site works. No error appears anywhere. GA4 shows a property with no data, which reads as "not set up yet" rather than "set up wrong". And whoever installed the container often was not the person who would notice the absence of reports.

What good looks like

One configuration tag for GA4, firing on all pages, with the measurement ID in a constant variable rather than typed into the tag.

Event tags for the key events, each with a specific trigger, and each named so a stranger can tell what it does: GA4 — form_submit — contact page beats Tag 7.

A published version, with a version note saying what changed and why.

Trigger conditions narrow enough to be correct. A form_submit trigger listening to all form submissions on the site will fire on the newsletter box in the footer.

The thing to check quarterly

Open the container's version history. If the latest published version is older than the latest change, someone left work unpublished. If the version notes are empty, nobody will ever be able to explain when something changed.

You can also see much of this from outside without any account access — a container's contents are served publicly, which is how a page can be audited for what its container actually contains. Useful for taking over an account whose credentials nobody can find.

The one-line summary for a client

"You have the delivery van. We need to check there is anything in it."