UTM parameters Urchin Tracking Module campaign tags

Definition

UTM parameters are query-string tags that web analytics tools read to attribute a session to a campaign. The name comes from Urchin, the analytics company Google bought in 2005 and whose product became Google Analytics. The five classic tags are utm_source (where the traffic comes from, such as a newsletter or a site), utm_medium (the type of traffic, such as email, cpc or social), utm_campaign (the campaign name), utm_term (the paid keyword) and utm_content (to tell apart ads or links inside one campaign). GA4 also reads utm_id, used to join imported cost data, plus utm_source_platform, utm_creative_format and utm_marketing_tactic.

UTMs only do something when a page running analytics receives them. An affiliate sending traffic to an advertiser through a network tracking link never sees the advertiser’s analytics; there the tags serve the advertiser, who may ask affiliates to add them so affiliate traffic is recognisable in their reports, or they are lost in a redirect. UTMs are most useful on the affiliate’s own properties: a content site, prelanders, newsletters and social profiles pointing to the affiliate’s own pages.

A UTM tag is not a click ID. It describes a group of visits, not a single one, so it cannot match a conversion to a click: thousands of clicks share the same campaign tags. That is also why Safari’s Link Tracking Protection removes click identifiers but leaves UTM tags untouched. Conversion credit with a network still runs on click IDs and postbacks; UTMs answer the analytics question of which channel and which campaign brought the traffic.

Consistency decides whether UTMs are worth anything. GA4 values are case sensitive, so Email and email become two sources, and a medium that does not match GA4’s default channel rules can push sessions into the Unassigned channel. Internal links between your own pages should never carry UTMs, because the site then appears as its own campaign and steals credit from the source that really brought the visitor. A shared naming sheet for the team prevents most of these problems.

In practice

Common mistakes

• Mixing capitalisation such as Email, email and EMAIL, which splits one source into several report rows.
• Using a medium value GA4 cannot map to a default channel, so the sessions land in Unassigned.
• Putting UTMs on internal links between your own pages, which makes the site look like its own traffic source.
• Expecting UTM tags to credit conversions on the advertiser’s site through a network link; that job belongs to click IDs and postbacks.
• Keeping no naming document, so campaigns from different months or team members cannot be compared.

Related terms

Go deeper

FAQ

Sources

1. URL builders: Collect campaign data with custom URLs — Google Analytics Help (support.google.com)
2. Default channel group — Google Analytics Help (support.google.com)
3. Campaign URL Builder — Google Analytics Demos and Tools (ga-dev-tools.google)
4. Link Tracking Protection in iOS 17 — 9to5Mac (9to5mac.com, 2023)

References are listed as plain text on purpose; look them up by title and publisher. Updated: 2026-10-09.