What Is utm_source? (Plus Source vs Medium, Settled)
The utm_source parameter defined, the source-vs-medium distinction that everyone gets wrong, and copy-paste examples per channel.
utm_source is the URL parameter that names the platform a click came from — google, beehiiv, linkedin, producthunt. It is the most-used and most-misused of the five UTM parameters, and the misuse is almost always the same one: confusing the source with the medium.
Source vs medium, settled
The rule that ends the confusion: source is the place, medium is the kind of place.
| Channel | utm_source | utm_medium |
|---|---|---|
| Your newsletter (on beehiiv) | beehiiv | |
| Google Ads | cpc | |
| Organic LinkedIn post | social | |
| Podcast sponsorship | lennys_podcast | podcast |
| Partner blog feature | partnersite | referral |
The classic mistake — utm_source=newsletter — breaks both layers at once: 'newsletter' is a medium hiding in the source field, and now your beehiiv and Mailchimp sends are indistinguishable while your email traffic no longer groups under one medium.
Three hygiene rules
- Lowercase, always. UTMs are case-sensitive strings; LinkedIn and linkedin are two sources in your reports.
- One canonical name per platform, forever. x or twitter — pick once, document it, never drift. A shared registry costs one spreadsheet.
- Source answers 'who sent this click?', never 'why?' — the why belongs in utm_campaign.
Where the value compounds
With first-touch persistence, the source captured on a visitor's first click survives to their signup and revenue — making revenue-by-source a filter instead of a forensic project. The full five-parameter system, naming conventions, and debugging checklist live in the complete UTM guide.