What are source and medium in GA4?
Source is who sent a visit (google, newsletter); medium is how (organic, referral, email). How GA4 sets them, and how to control them with UTM tags.
Source is where a visit came from, such as google, x.com or newsletter. Medium is what kind of link it was, such as organic (unpaid search), referral (a link on another site) or email. GA4 often shows them together as source / medium: google / organic.
Common values
| Source / medium | Means |
|---|---|
google / organic | Unpaid Google search |
google / cpc | Google Ads |
(direct) / (none) | No referrer and no tags: typed, bookmarked, or hidden by an app |
news.ycombinator.com / referral | A link on another site |
newsletter / email | A link you tagged with UTM tags |
chatgpt.com / referral | A link in ChatGPT |
How GA4 sets them
- If the link has UTM tags, GA4 uses them:
utm_sourceandutm_medium. - Otherwise, GA4 reads the referrer (the page the visitor came from) and decides: a search engine becomes
organic, other sites becomereferral. - With neither, the visit is
(direct) / (none).
Session, first user and event
GA4 has several versions: Session source (where this visit came from), First user source (where the person first came from) and plain Source (used for key event credit). Traffic acquisition uses session source; User acquisition uses first user source.
In SimpleDash
The Sources card shows session source, and Channels groups them. Default channel group.
Related
Last updated
Events
In GA4, everything is an event: page views, clicks, signups, purchases. The four kinds of events, which you get automatically, and how they become key events.
Default channel group
GA4 sorts every visit into a channel, such as Organic Search, Direct, Referral or Email, using rules on source and medium. Each channel in plain words.