UTM parameters

A UTM parameter is a label you write. You decide that this link is source=newsletter and medium=email, you append it, and your analytics groups the visit accordingly.

That is the whole mechanism, and it explains both the strength and the limit. UTMs work anywhere, in any channel, including ones that have no advertising platform behind them — a podcast mention, a printed QR code, a partner’s link. Nothing has to support them.

The confusion worth clearing up. A UTM and a click ID look similar sitting next to each other in a URL and do entirely different jobs:

• A UTM is descriptive text that you invented. It says how you want this traffic filed. No system can verify it, and nothing connects it to a specific click.
• A click ID is an opaque token the platform generated. It identifies one particular click in that platform’s records, and it is what makes a conversion matchable back to an ad.

So UTMs answer “which campaign should this visit be grouped under” in your reports. Click IDs answer “was this the person who clicked that ad” for the platform. Neither substitutes for the other, and a link carrying only UTMs will show up correctly in your analytics while remaining unattributable in the ad platform.

Where they break. They are typed by hand, so they drift — Email, email and e-mail become three sources. They are visible in the address bar, so they end up in shared links, bookmarks and screenshots, crediting a campaign for traffic it never sent. And appending them to internal links restarts the visit as a new campaign, which corrupts the very reports they exist to produce.