The utm_source you should NOT use for Meta Ads (and why GA4 makes it disappear)

A lot of marketers — myself included, at first — tag their Meta (Facebook / Instagram) ad URLs with utm_source=meta . It feels natural: the company is called Meta now, right? But if you open Google's officially distributed GA4 Default Channel Group Source Categories spreadsheet and search through all 819 entries, you'll find something strange: facebook is there fb is there facebook.com is there instagram is there meta is not That one missing line isn't a trivia item. It's the difference between