How Google Analytics 4 works
GA4 is the current version of Google Analytics, and it replaced Universal Analytics rather than upgrading it. The change that matters is the data model. Universal Analytics organised everything around sessions and pageviews; GA4 records a stream of events, each one an action with a name and a set of parameters describing it. A page view is simply one event among many.
Data arrives through a data stream — one for a website, another for an app — and the tag on the page sends events into it. Some events are collected automatically, some are switched on in the stream’s enhanced measurement settings, and the rest you define yourself. Once inside, reporting splits between standard reports for the usual questions and Explore for building your own tables, funnels and path analyses.
Two other properties are worth knowing early. GA4 can measure a website and an app in the same property, which older versions could not. And it applies modelling and thresholding, so certain figures are estimates rather than raw counts, particularly where consent is missing or where a small report would otherwise identify individuals.
Why GA4 matters
It is free, it is the default, and it is the layer everything else plugs into: audiences exported to Google Ads, conversions imported into bidding, dashboards assembled in Looker Studio. Even businesses that dislike it end up depending on it, because the alternatives rarely connect as cleanly to the ad accounts.
It also decides which questions you can answer later. Analytics only shows what it recorded, and GA4 keeps event-level detail for a set retention period rather than indefinitely, so a measurement plan skipped at launch turns into a gap you cannot fill retrospectively.
Common mistakes with GA4
The commonest is installing the tag, seeing traffic appear and stopping there. A default install counts visits. It does not know that a WhatsApp tap, a phone call or a booking is what your business lives on, and nothing meaningful is measured until you tell it.
Next comes comparing GA4 with the old numbers and panicking. Sessions, users and bounce are defined differently now, so a moved figure often reflects the new definition rather than the business. After that come the quiet ones: leaving your own team’s visits in the data, never setting the reporting time zone or currency, and never registering event parameters as custom dimensions — so useful detail is collected but stays invisible in reports.
How to act on it
Treat setup as a short project rather than a checkbox. Write down the actions that represent value, implement them as events, mark the important ones as key events, and confirm each in DebugView before anyone reports on them. Set the time zone, currency and data retention on the first day, exclude internal and developer traffic, and link Google Ads and Search Console.
Then agree what will actually be reported. Choose a handful of measures the business will act on, build one dashboard around them, and resist wandering through every report each month. Where an account has been inherited rather than built, auditing the GA4 configuration is usually faster than trying to reconcile numbers nobody can explain.