Setup Guide
Two IDs. Two completely different jobs.
Container ID
GTM-XXXXXXXX
GTM-
identifies a Tag Manager container
XXXXXXXX
your unique container ID
goes into
Your HTML snippets: both the <script> in head and the <noscript> in body
job
Loads the GTM container on your site so Tag Manager can fire all your tags
where to find it
GTM Dashboard
→
Admin
→
Container Settings
≠
Measurement ID
G-XXXXXXXXXX
G-
identifies a GA4 property
XXXXXXXXXX
your unique property ID
goes into
The GTM tag configuration: the Tag ID field inside your Google Tag setup in GTM
job
Tells GTM which GA4 property to send data to when the tag fires
always confirm from here, not any other screen
GA4 Admin
→
Data Streams
→
Your stream
→
Measurement ID
⚠️
The most common mistake: GA4 shows Measurement IDs in multiple places during setup. Always confirm from Admin → Data Streams → your stream. IDs from other screens can silently point to the wrong property.