What Is a GA4 Measurement ID?
A GA4 Measurement ID is the identifier, formatted G-XXXXXXXXXX , that connects a website's tracking code to a specific Google Analytics 4 property.
Why It Matters In TrafficCreator#
TrafficCreator uses your GA4 Measurement ID to tag delivered traffic so it appears in your GA4 dashboard. Only G- IDs are accepted — Google Tag Manager (GTM-) and Universal Analytics (UA-) IDs are rejected, and the format is strict: G- followed by exactly 10 letters or digits.
It is required, not optional. On the Economy, Professional and Expert tiers a campaign will not start without a valid Measurement ID — it stays in a pending_ga state and delivers nothing. Only GSC and Local SEO campaigns are exempt, since those are measured in Search Console. See Create your first campaign.
Example#
G-ABC1234567 entered in a project's GA4 field lets that project's traffic show up in the matching GA4 property.