UTM Builder

How the UTM Campaign URL Builder works

UTM builder: the five parameters

UTM parameters are five query-string keys that Google Analytics, and nearly every other analytics tool, reads to attribute a visit to a campaign. They were named after Urchin Tracking Module, the product Google bought in 2005, and they have survived unchanged because they are simple: the link carries its own provenance, and no cookie, pixel or referrer header is required.

The three you must set. utm_source names where the click came from: newsletter, google, linkedin, partner-site. utm_medium names the kind of channel: email, cpc for paid search, social, display, referral, affiliate. utm_campaign names the specific push: spring-sale, product-launch, webinar-june. Google Analytics 4 requires source and medium for the visit to be attributed as a campaign at all; without them the click falls back to whatever the referrer suggests, which for email is usually nothing and gets logged as direct traffic.

The two you might set. utm_term was built for paid search keywords and is still mostly used that way. utm_content distinguishes links within the same campaign — header-button versus footer-text, or variant-a versus variant-b — which is how you learn that nobody clicks the footer. Leave them blank when you have nothing to say; empty parameters clutter the link and confuse reports.

Why case and spacing matter more than you would think. Analytics tools treat parameter values as opaque strings. Email, email and e-mail are three separate mediums; Spring Sale and spring-sale are two campaigns; a stray trailing space makes a fourth. Every one of those splits your numbers, and it is far easier to be consistent when the link is generated than to merge rows in a report later. The default here lowercases every value and replaces spaces with hyphens. Switch it off only if your team already has a convention that depends on capitals.

Encoding. Anything outside the plain URL character set — spaces, ampersands, accented letters, plus signs — has to be percent-encoded or the link breaks or, worse, silently truncates at the first &. The builder uses the browser's own URL parser to do this, so what you see is exactly what a browser will send. If the landing page already has a query string, the UTM parameters are added to it rather than replacing it, and an existing UTM parameter is overwritten rather than duplicated.

Where UTMs belong, and where they do not. Use them on links you control that point to your own site from somewhere your analytics cannot otherwise see: emails, social posts, paid ads, QR codes, print, partner placements. Do not use them on internal links between pages of your own site; that restarts the session with a new source and destroys the original attribution. And do not use them on links to other people's sites, which achieves nothing for you and litters their reports.

Keep a record. The link carries the parameters but not the meaning. A shared spreadsheet of every tagged URL, with who created it, for what, and when, is the boring habit that makes the reports interpretable a year later when nobody remembers what campaign-7b was.

UTM link worked examples

The formula: tagged URL = page URL + ? + utm_source=… & utm_medium=… & utm_campaign=…, then the optional utm_term and utm_content, each value URL-encoded.

First example. The page https://example.com/shoes with source newsletter, medium email and campaign spring-sale gives https://example.com/shoes?utm_source=newsletter&utm_medium=email&utm_campaign=spring-sale.

Second example. The same link with content Header Banner and the lowercase option off gives …&utm_content=Header+Banner, because a space is encoded as +. With the option on it becomes utm_content=header-banner.

How many parameters are there? Five: utm_source, utm_medium and utm_campaign are required, and utm_term and utm_content are optional.

Common source and medium pairs and the GA4 default channel they land in

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