What is GA4?

GA4 records what happens on your website after someone arrives: which pages they saw, how long they stayed, whether they tapped the phone number, whether they sent a form. Google Ads reports the click; GA4 reports everything after it.

It replaced Universal Analytics, which stopped processing data in 2023, and it works differently enough to catch people out. Where the old version counted sessions and pageviews, GA4 counts events, so almost every metric people were used to has either changed definition or gone.

It is the record that outlives an advertising campaign. Ad accounts get rebuilt and agencies get changed, but a properly configured Analytics property keeps a continuous history of what your website did, which is the only way to tell whether this quarter is genuinely better than last.

It is also the second opinion. When an ad platform reports its own performance, it is marking its own homework. GA4 sees traffic from every source, so it can show whether the paid campaign added enquiries or simply took credit for people who would have found you anyway.

The property should be in your business's own Google account, with your agency given access rather than ownership. This is the single most common thing to get wrong at setup and the most expensive to discover later, because a property cannot be moved out of someone else's account on request.

Beyond that, most of GA4 is not worth your attention. The two events that matter are a tap on the phone number and a form the server actually accepted. Sessions and engagement rate make a report look thorough; neither of them is a job in the schedule.