Knowing What Works: UTM Links

Why analytics often cannot tell

When someone clicks a link in your newsletter, a PDF or a messaging app, the visit often arrives without clear information about where it came from. GA4 may then record it as direct, unassigned or a vague referral. After a campaign you cannot tell whether the newsletter or the social post brought the bookings. UTM parameters fix this. They are short labels added to the end of a link. Analytics tools read them and record where the visit came from.

https://velo-kessler.ch/spring-check?utm_source=instagram&utm_medium=social&utm_campaign=spring_check_2026

The question mark starts the parameters. Each parameter is a name, an equals sign and a value. An ampersand (&) separates them. The page itself does not change. The visitor sees the same page as without the tags.

The five parameters

Always set source, medium and campaign. Content and term are optional. GA4 also reads a few further parameters, such as utm_id, but you can do good work without them.

Rules that keep your data clean

• Always use lowercase. GA4 treats 'Newsletter' and 'newsletter' as two different sources, so your report splits in two.
• No spaces. Use underscores or hyphens, as in spring_check_2026.
• Use standard medium names. GA4 sorts traffic into default channel groups such as Email, Organic Social and Paid Search, partly based on the medium. 'email' lands in Email. An invented medium such as 'mailing' may end up as Unassigned.
• Write your naming rules down in a simple shared sheet and reuse them. Consistency matters more than the exact words.

Google Ads does not need manual UTM tags when auto-tagging is on and the Ads account is linked to GA4. Ads adds its own click identifier, and GA4 reads the campaign details from it. Manual tags are for everything else: email, social posts, partners, QR codes.

The common mistake

Putting UTM tags on links inside your own website, for example on a home page banner that links to the booking page. When a visitor clicks it, GA4 records a new traffic source for that visit. A customer who came from Google search now looks like they came from 'banner'. Your real sources get overwritten. UTM tags belong only on links that point to your site from outside. To measure internal banners, use GA4 events or reports on page paths instead.

Do this now

Pick the next link you will share outside your site: a newsletter, a social post or a QR code on a flyer. Build it with source, medium and campaign, all in lowercase. Google's free Campaign URL Builder can help. Open the finished link once to check that the page loads. A few days later, open the Traffic acquisition report in GA4 and look at session source / medium. Naming conventions and Google Tag Manager in depth are covered in the course Tracking, Tag Manager & Consent.