What is utm_source=fb?

Who adds it

It usually comes from Meta's dynamic URL parameter {{site_source_name}}, which advertisers place in their ad's URL parameters. Meta fills it with fb for Facebook placements. Google's UTM guidance also uses fb as an example value for Facebook.

What it means

The visit came from a Meta ad that ran on Facebook. The click usually also carries an fbclid and an l.facebook.com or lm.facebook.com referrer.

What to do with it

The same campaign can also produce ig, msg, an or th values for other placements, so group them if you want a Meta total. GA4 counts it as Paid Social only if fb is on its list of social sources and the medium matches the paid pattern.

How Vireo shows it

Vireo Pro's UTM campaigns card lists tagged visits by Source, Medium and Campaign, with visitors and pageviews. The tags are read from the first page of each visit, and the same tags feed revenue by source.

In the free plugin, Vireo drops the query string from page addresses, keeping only a few WordPress ones such as p and page_id, so a tagged URL counts as the same page as the untagged one. The visit is counted under the referrer it arrived with.

When a link carries utm_source with no utm_medium, as ChatGPT's do, Pro's revenue attribution takes the medium from the referrer's source group. With no referrer either, it's labelled campaign.

UTM campaigns are part of Vireo Pro. See UTM campaigns in the docs.

Sources

Specifications For URL Dynamic Parameters - Meta Business Help Center

use fb for Facebook and insta for Instagram to maintain granular reporting.

URL builders: Collect campaign data with custom URLs - Analytics Help

Paid Social Source matches a regex list of social sites AND Medium matches regex ^(.*cp.*|ppc|retargeting|paid.*)$

Default channel group - Analytics Help