UTM Parameters

UTM parameters are little tags you add to the end of a link that tell GA4 where the click came from. The three core ones are utm_source, utm_medium, and utm_campaign (with optional utm_term and utm_content). They're how any link you control — in an email, a social post, a QR code — gets attributed correctly instead of vanishing into direct.

Why it matters

GA4 can only attribute traffic it can identify. For search and referral links it usually manages on its own, but for the links you share, it needs you to label them. UTM tags are that label. They're the single highest-leverage habit a small business can adopt to make its analytics honest — the difference between knowing your newsletter works and merely hoping it does.

A concrete example

You build your newsletter link as yoursite.com/offer?utm_source=newsletter&utm_medium=email&utm_campaign=spring-launch. In GA4, that click now arrives as source/medium newsletter / email under the campaign "spring-launch." You can see precisely how many sessions, engaged visits, and key events the send produced — instead of watching them dissolve into direct.

The common misreading

The mistake is inconsistent tagging, which is almost worse than none. Email and email become two separate mediums because UTMs are case-sensitive; news and newsletter split your data in half. Pick one lowercase convention and reuse it everywhere. And never UTM-tag internal links between your own pages — it resets the session and corrupts your source/medium attribution.