Table of Contents
utm_medium describes how a visitor arrived, such as through email or a paid campaign. GA4 uses it alongside other traffic-source information to assign channels. This guide explains common values and what to check when the channel differs from your expectations.
What Is utm_medium?
In GA4, utm_medium populates the Session medium and First user medium dimensions. Unlike utm_campaign, which can be tailored to your company's product hierarchy, utm_medium is one of several inputs used for default channel classification. If its value does not match a current channel definition, another definition may still apply based on the other available traffic-source information; otherwise, GA4 can report the session as Unassigned.
The GA4 Default Channel Grouping Matrix for utm_medium
The table below gives examples of medium values used by Google's current default channel definitions. Channel assignment also depends on other traffic-source information; check Google's current definitions before relying on a particular mapping.
| Target GA4 Channel Group | Example utm_medium Values | Other Information That Can Affect the Match |
|---|---|---|
| Paid Search | cpc, ppc, paidsearch |
Source must match a recognized search site list (e.g. google, bing, yahoo). |
| Paid Social | paid_social, paidsocial, paid-social, cpc, ppc |
Source must match Google's predefined social site list (meta, facebook, linkedin, etc.). |
| Organic Social | social, social-network, social-media, sm |
Or source matches Google's social list and medium is empty/referral. |
email, e-mail, e_mail, newsletter |
Source is optional (any source will classify under Email). | |
| Affiliates | affiliate, affiliates |
Direct match to medium string. |
| Display | display, banner, cpm, expandable |
Must not match Paid Social or Paid Search sources. |
| Paid Other | cp, cpa, cpp |
Catch-all for paid campaigns that don't match Search/Social/Display. |
The Paid Social Dilemma: paid_social vs cpc
Many media buyers who manage both Google Ads and Meta Ads default to tagging Meta links with utm_medium=cpc. While GA4 will technically map facebook / cpc into "Paid Social" because Facebook is on Google's recognized social sites list, using cpc on social platforms creates reporting confusion:
One naming approach is to use cpc for paid search and paid_social for paid social. Treat this as a team convention, then check the source and medium against GA4 channel rules. Medium alone does not determine every channel.
How Rogue Mediums Create "Unassigned" Traffic
A custom medium such as utm_medium=influencer-collab or utm_medium=podcast_sponsor may not match a default channel definition by itself. Classification depends on the other available traffic-source information and the applicable rules. Use a documented naming convention, check Google's current definitions, and consider a Custom Channel Group when you need a distinct reporting category.
For the broader setup, read Complete UTM Parameters Guide for GA4: Manual Campaign Dimensions & Best Practices. Browse the UTM Parameters guides to choose another troubleshooting task.
References
- Default Channel Grouping Definitions in GA4 (Google Analytics Help)
