GA4 Pipeline -Episode 2: Sending Events | How Data Leaves Your Site
Previous Episode 1: Define | Google Tag Manager
In episode 1, we looked at where events are defined. Now we move to the next step in the pipeline: Send
This is the moment data actually leaves your website or app.
What “send” means in GA4
Once an event is defined, it still needs to be delivered.
This happens through:
- gtag.js for websites
- GA4 SDKs for mobile apps
This layer is responsible for sending events. Nothing more.
It does not decide:
- Which events are important
- Whether the data makes sense
- How it will be analyzed
It sends exactly what it is given.
A simple scenario
An event has already been defined:
- Event name: page_view_pricing
- Trigger: page load
- Metadata: page URL
When the page loads:
- The trigger fires.
- The event is packaged.
- The event is sent to GA4
No interpretation happens here.
Where gtag fits
When Google Tag Manager is installed, the site loads a small script from Google.
This script:
- Pulls the latest GTM configuration
- Applies the defined events and triggers
- Uses gtag to send events when conditions are met
The code stays the same.
The configuration changes.
What the send layer actually does
- Packages the event
- Attaches metadata
- Sends it at the moment the trigger fires
That’s it.
It does not:
- Validate business meaning
- Clean data
- Fix modeling mistakes
If an event is poorly defined, it will still be sent faithfully.
Why this separation matters
When something looks wrong in GA4, the send layer is often blamed.
In practice, most issues come from:
- Unclear event definitions
- Triggers firing at the wrong time
- Incomplete or noisy metadata
The send layer does not correct upstream decisions.
Common misconceptions about gtag
- gtag does not decide what events exist
- gtag does not improve data quality
It transports events.
Everything else is handled downstream.
How this fits in the pipeline
- Define decides what an event is
- Send decides when it leaves the site
- Everything after that happens downstream
Each layer has a narrow responsibility by design.
If GTM shapes your data model, the send layer simply moves it forward.
Nothing more. Nothing less.
What’s Next?
After events are sent, they disappear from view.
What happens next is the most opaque part of GA4.
In the next episode, we’ll look at collection; how GA4 receives events, applies processing, and why the data you see later is not stored exactly as it was sent.