Are UTM parameters case sensitive?
Yes in GA4. Use lowercase consistently for every value, and enforce it with a link-builder template rather than trusting each campaign owner to remember.
What is UTM parameters?
Also called: UTM tags, campaign parameters, utm_source
The three required parameters are utm_source (which property, e.g. newsletter), utm_medium (which channel type, e.g. email), and utm_campaign (which initiative). Analytics channel groupings key on utm_medium in particular, so an invented medium value drops the traffic into "unassigned".
UTM values are case-sensitive in GA4. Facebook, facebook, and FaceBook are three separate sources in your reports, and the split is not recoverable after collection. Lowercase everything, always.
UTMs belong on external inbound links only. Putting them on internal links restarts the session attribution, overwriting the real acquisition source with your own internal navigation.
Why it matters
UTM discipline is the cheapest attribution improvement available — no code, no vendor, no consent implications — and inconsistent tagging is the single most common reason a channel report is unusable.
Common questions about UTM parameters
Should I use UTM parameters on Google Ads links?
Use auto-tagging (the gclid parameter) instead — it captures more detail and reconciles correctly with Google Ads reporting. Manual UTMs on Google Ads links can override auto-tagging and lose data.
Related terms
- Attribution windowAn attribution window is the period after an ad interaction during which a resulting conversion is still credited to that interaction.
- GA4 key eventsKey events are the GA4 events you have marked as business-critical — purchases, sign-ups, qualified leads.
- PII leakagePII leakage is the accidental transmission of personally identifiable information — email addresses, phone numbers, names, order-level customer details — into an analytics or advertising platform that is not permitted to receive it.
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