Ad glossary · Tracking and data · Checked 2026-10-23
What is GA4: events, key events and how advertisers use it
GA4 is Google’s analytics tool for websites and apps, collecting data based on events rather than sessions; the old Universal Analytics stopped processing data on 1 July 2023.
- English
- Google Analytics 4 (GA4)
- Also called
- Google Analytics 4, Google Analytics
- Area
- Tracking and data
How it is used
For Meta advertisers, GA4 is a second set of books that belongs to no ad platform: split traffic by UTM, see what happens after arrival (where people leave, which checkout step loses them), and reconcile it with Meta and your store.
| Kind | Where it comes from | Do you implement it? |
|---|---|---|
| Automatically collected | Collected by default once GA4 is set up | No |
| Enhanced measurement | Collected once enhanced measurement is on for the data stream | No code; switch the options on |
| Recommended | Google predefines the name and parameters, such as purchase | Yes |
| Custom | Events you define; most standard reports do not show them | Yes |
Everything is an event
GA4 records page views, scrolls, clicks and purchases all as events.
Each event carries parameters such as value and currency. Some are collected automatically, some come with enhanced measurement, and recommended events such as purchase you implement yourself; the table above sets out the four kinds.
An event arriving is not an event you can report on.
To count it as a conversion, mark it as a key event. To group by a custom parameter, register it as a custom dimension, which takes 24 to 48 hours to become usable.
Why GA4 and Meta never agree
They use different attribution rules (Meta its own attribution setting, GA4 data-driven or last-click models), identify people differently, and are blocked by different things (ad blockers, consent settings).
The job is not to make them match. Separate Meta traffic in GA4 with UTMs and log the gap once a week.
A stable gap means both are usable. A sudden jump means one side’s tracking broke; check whichever side changed most recently.
Example
Launch check: in GA4’s Realtime report, click through from your own ad and complete a purchase; confirm the purchase event carries the right value and that purchase is marked as a key event.
Engagement turns on 10 seconds: a one-page session longer than 10 seconds still counts as engaged. 620 engaged out of 1,000 sessions is a 62% engagement rate and a 38% bounce rate.
Not to be confused with
GTM: GTM is where tags are deployed, GA4 is where data is collected and reported. A common setup installs GA4 through GTM.
FAQ
How is GA4 different from Universal Analytics?
GA4 is built on events; Universal Analytics was built on sessions and page views. Standard Universal Analytics stopped processing data on 1 July 2023, so every new setup is GA4.
Do I have to install GA4 through GTM?
No. The Google tag can go straight into the site; GTM just makes several tags easier to manage.
Where the course puts it to work
- Intermediate, chapter 2: GA4 setup and events
- Intermediate, chapter 7: Reading GA4: traffic, the shopping funnel and three-way reconciliation
Official sources
We read each page below on 2026-10-23 and built the definition from it.
- Introducing the next generation of Google Analytics · Checked 2026-10-23
- About events · Checked 2026-10-23
- Measure ecommerce · Checked 2026-10-23
- About Attribution Models and Attribution Settings · Checked 2026-10-23