Short answer
UTM parameters are labels added to the end of a link, such as utm_source and utm_campaign. When someone clicks it, Google Analytics reads the labels and records which campaign sent them. Always set source, medium and campaign, keep values lowercase, and never put them on links inside your own site.
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What a UTM link looks like
It is an ordinary web address with extra pieces after a question mark. For example, a link to a shop page with utm_source=facebook, utm_medium=paid_social and utm_campaign=diwali_sale added to the end.
The visitor sees the same page. Google Analytics sees where they came from, because it reads those labels the moment the page loads.
The parameters, one by one
utm_source: where the click comes from, such as facebook, newsletter or whatsapp.
utm_medium: the kind of traffic, such as cpc, email, social or paid_social.
utm_campaign: a name you will recognise in a report, such as diwali_sale_2026.
utm_term: the keyword, mostly for search ads.
utm_content: tells two ads or links in the same campaign apart.
utm_id: an optional campaign ID that ties the click to ad platform data.
Source, medium and campaign are the three to set every time.
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Where the data shows up in Google Analytics 4
In GA4, open Reports, then Acquisition, then Traffic acquisition. Change the table's first column to session source and medium, or to session campaign, and your tagged links appear there.
Use standard values for medium, such as cpc, email, social and paid_social. GA4 sorts traffic into channels from the medium and source, and an unusual word can drop your traffic into the wrong channel.
The mistakes that split your data
Capital letters. GA4 treats Facebook and facebook as two different sources, so your reports split in two. Use lowercase everywhere.
Spaces. They turn into %20 in the link and make values harder to match. Use underscores.
Inconsistent names. Newsletter, email_newsletter and mailer are three separate sources. Choose one name and keep it in a short shared list.
UTMs on internal links. A tagged link inside your own site can start a new session and overwrite where the visitor really came from. Use UTMs only on links that bring people in from outside.
UTMs and Google Ads
Google Ads has its own tagging called auto-tagging, which adds a gclid to the link and connects the click to Google Analytics. For Google Ads you usually do not need UTMs. Add them only if you know why, because mixing the two can cause confusion.
For other platforms, such as Facebook and Instagram ads, email, WhatsApp, QR codes and social posts, UTMs are how you tell the sources apart.
A UTM link only tells you the click
The label records where a visitor came from. Whether the sale at the end is credited to it depends on tracking that survives the checkout. Third-party checkouts and payment pages are where tracking is most often lost, so a clean UTM link can still show no revenue.
If a campaign shows clicks but no orders you can match, the cause is usually tracking, not the campaign.