Google Tag Manager.

What is Google Tag Manager?

Google Tag Manager (GTM) is a free Google tool for adding and managing tracking code, known as tags, on a website without editing the site's code each time. You install one GTM container on every page, then add tags for GA4, Google Ads or other platforms inside GTM.

Triggers decide when each tag fires, such as on every page view or only when a form is successfully submitted.

Why it matters

Tracking needs change constantly: a new campaign, a new form, a new ad platform, updated consent rules. Without Tag Manager, each change needs a developer and a site release, so tracking falls behind and decisions are made on gaps. With it, a competent marketer can add and test tracking in an afternoon. It also keeps every tag in one auditable place, which matters when you need to show exactly what fires before a visitor gives consent.

How it works

• The container A single snippet on every page of your site that loads whatever you have configured in GTM.
• The tags The pieces of tracking code themselves, such as the Google tag for GA4 or a Google Ads conversion tag.
• The triggers Rules for when a tag fires, for example a click on a phone number or a successful form submission.
• The variables Values GTM reads from the page, such as a form ID or order value, to make tags and triggers precise.
• Preview and versions Changes can be tested in preview mode before publishing, and earlier published versions can be restored.

What to do about it

Check who has access to your GTM account and remove anyone who has left, including former agencies and freelancers. Make sure the account is owned by your business rather than a supplier. Open the container and list every tag: what it does, who added it, and whether it still matters. Pause anything nobody can explain, test in preview mode, and publish with a clear version note. Do this tidy-up before adding anything new.