UTM URL builder

What UTM parameters do

UTM (Urchin Tracking Module) parameters are tags appended to a link's query string that tell your analytics tool where a click came from. The name is a fossil of Urchin, the company Google bought in 2005 to build Analytics. When someone follows a tagged link the parameters ride along in the URL, and your platform reads them on arrival — so you can compare a newsletter, a paid ad and an organic social post side by side instead of seeing them lumped together as anonymous traffic. They're read entirely client-side by the analytics script; nothing about the tagging itself touches a server here.

The five tags and how GA4 uses them

There are five standard parameters. The core trio is utm_source (where the traffic originates — newsletter, google, facebook), utm_medium (the channel type — email, cpc, social), and utm_campaign (the initiative — spring_sale). Two are optional: utm_term for paid keywords and utm_content to tell apart two links in the same email or two creative variants in an A/B test. In Google Analytics 4 these map to the Session source, Session medium and Session campaign dimensions, and the medium value is what GA4 uses to bucket a visit into its default channel groupings — mislabel it and the visit lands in the wrong channel.

Naming conventions and pitfalls

UTM values are case-sensitive: Email, email and EMAIL become three separate rows in your reports, which is why the lowercase toggle above defaults on. Pick a fixed vocabulary for source and medium and never improvise per campaign, or your data fragments. Two rules worth burning in: never tag internal links between pages of your own site — doing so restarts the session and wrongly re-attributes the visit — and never put personal data (emails, names) in a UTM, since the full URL lands in analytics and server logs. This builder preserves any query parameters already on your URL and only appends the UTM tags.