Conversion & attribution
What is Measurement Protocol?
GA4’s server-to-server API for sending events directly to a property without a browser — used for server-side events and offline data.
Definition
The GA4 Measurement Protocol is an API for sending events to a GA4 property directly from a server, bypassing the browser. It’s how server-side events, backend purchases, and offline interactions reach GA4.
Each hit needs the property’s measurement ID and an API secret, and — to attribute correctly — the same client ID and session ID the browser used, which is the part most implementations get wrong.
Why it matters for agencies
It’s the mechanism behind a lot of server-side tracking and refund/subscription event capture. Done right, it makes GA4 reflect real backend outcomes; done wrong, it creates duplicate or unattributed events.
Agencies advising on server-side setups need to know where the Measurement Protocol fits and what it can’t do (it won’t magically fix client-ID stitching) so they don’t oversell it.
Measurement Protocol in Phloz
Phloz models server endpoints and the conversion-API endpoints that use the Measurement Protocol as nodes, and flags an isolated server endpoint that isn’t connected to anything — a classic "we set up server-side but nothing routes through it" gap.
Frequently asked questions
- Is the Measurement Protocol the same as server-side GTM?
- No. Server-side GTM is a container that runs on your server; the Measurement Protocol is GA4’s API for receiving events. A server-side GTM container often sends to GA4 via the Measurement Protocol, but they’re different things.
- Why do Measurement Protocol events sometimes not attribute?
- Almost always a client-ID/session-ID mismatch — the server hit doesn’t carry the same identifiers the browser used, so GA4 treats it as a separate, unattributed user. Stitching those IDs is the hard part.
Related terms
Other tracking-infrastructure concepts agencies run into alongside this one.
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