UTM Builder

How it works

The base URL is parsed with the browser's own URL API, which is why you get an error until you include https://: the parser needs a scheme, and it's the same parser your browser uses for real navigation, so if it accepts the URL here, the URL works. Each of the five utm_ values is then applied through searchParams.set(), which percent-encodes special characters automatically (a campaign named spring sale becomes spring+sale in the query string, an ampersand becomes %26 instead of splitting your parameter in two). Using set() rather than string concatenation also means query parameters already on the URL are preserved, clearing a field removes its parameter instead of leaving an empty utm_term= behind, and a #fragment stays where it belongs, after the query string.

The mistake that quietly ruins campaign reports: UTM values are case-sensitive in analytics. GA4 will happily show email, Email, and EMAIL as three separate sources, splitting one campaign's numbers three ways. Pick all-lowercase and never deviate. It also pays to keep utm_medium inside the vocabulary GA4's default channel grouping recognizes, like email, cpc, social, or referral; invent something creative and your traffic lands in the Unassigned bucket where nobody looks.

The URL is assembled locally on every keystroke and is never requested, pinged, or logged by this page. Open the DevTools Network tab and type away: nothing fires. The finished link only travels anywhere when you paste it into your campaign.