UTM parameters

UTM parameters were introduced by Urchin (acquired by Google in 2005 to become Google Analytics). They live in the URL as query parameters: ?utm_source=youtube&utm_medium=video&utm_campaign=spring-tech-review. When a visitor clicks, the analytics tool on the destination site reads the parameters and records the session as originating from those values. UTM parameters are purely analytics-side; they do not affect merchant-side processing or affiliate commission attribution.

The five UTM parameters. utm_source identifies where the traffic comes from (youtube, newsletter, twitter). utm_medium identifies the channel type (video, email, social, cpc). utm_campaign identifies the marketing initiative (spring-tech-review, q2-launch). utm_content distinguishes variants within a campaign (pinned-comment vs description). utm_term is historically used for paid-search keywords and is rarely used outside of that. Three are essential (source, medium, campaign); two are optional.

Naming conventions and pitfalls. UTM values are case-sensitive in Google Analytics. Newsletter and newsletter are tracked as separate sources, which fragments your reports for months before anyone notices. Stick to lowercase everywhere. Use hyphens, not underscores or spaces. Use the same medium values across all campaigns (do not mix email, Email, and e-mail). Document your taxonomy somewhere your future self can find it; nothing rots faster than a UTM scheme that was clear at launch and incomprehensible six months later.

The UTM hierarchy in analytics reporting. Google Analytics (GA4 and earlier) builds traffic reports by stacking these parameters. Source/Medium is the primary breakdown ("youtube / video"). Campaign segments further within source/medium ("youtube / video / spring-tech-review"). Content and term add another layer for the rare cases that need it. A well-tagged URL gives you four or five layers of attribution depth in one report.

UTM versus <a href="/glossary/sub-id" class="font-medium text-ab-violet underline decoration-ab-violet/30 underline-offset-4 transition-colors hover:decoration-ab-violet">sub-ID</a>: when to use which. Sub-IDs answer "which of my placements converted into a sale?" (the affiliate network's view). UTMs answer "which of my placements sent the traffic?" (your analytics view). For a link that goes directly to a merchant, only the sub-ID gives you per-placement revenue data. For a link that goes through your own site (with an affiliate redirect downstream), use both: UTM to track traffic to your site, sub-ID to track conversions on the merchant.

UTMs and affiliate-link redirect chains. UTMs survive redirects only if every hop preserves query parameters. Affiliate networks vary: some pass UTMs through cleanly, some strip them, some rewrite them. Test by clicking your own UTM-tagged affiliate URL in an incognito window and checking what arrives at the destination. If the UTM parameters are gone by the final URL, your analytics will undercount that source. The fix is to put UTMs on the managed URL wrapper if you control one, so the analytics attribution happens before the affiliate redirect chain.

Do UTMs affect affiliate tracking? No, with one caveat. The merchant's affiliate-tracking system does not read UTM parameters; it reads the affiliate tag or click ID. UTMs and affiliate parameters live in the same query string but in separate ecosystems. The caveat: if a particularly aggressive merchant strips all unrecognised query parameters at their entry point, your UTMs could be lost on the way to the destination. The affiliate tag almost always survives because the merchant whitelists it; UTMs are not whitelisted.

UTMs in the GA4 era. GA4 reads UTMs identically to legacy Universal Analytics, but the reporting interface is different. Source/medium reports live under Acquisition → Traffic acquisition. Campaign-level breakdowns require slightly more clicking. The underlying URL tagging convention has not changed since 2005; if you tagged campaigns correctly in 2010, the same URLs still work in 2026.