Google Analytics 4 Setup | A Correct Measurement Base
GA4 setup is often assumed to be adding a snippet to the site. Once the code is in, data starts flowing, charts appear, and it looks finished. The real setup begins after that: which actions get measured, which count as key events, and how the data connects to the advertising side.
What the default setup does not measure
Out of the box GA4 collects automatic events such as page views, scrolls and outbound link clicks. These describe the shape of your traffic but say nothing about your business.
What matters to you is a form submission, a phone call, a WhatsApp tap or a purchase. None of these are measured by default; each has to be defined separately. The most common picture I find in audits is a GA4 property that has been collecting data for months without measuring a single real conversion.
Choosing key events
When you mark an event as a key event in GA4, it starts counting as a conversion. That decision affects every report afterwards, and your Google Ads bidding strategy.
A frequent mistake is marking too many events as key events. When page views or scrolls become key events, the conversion count looks high but means nothing; connected to the advertising side, the algorithm starts hunting for the wrong person. A key event should be the action that actually earns money.
The Google Ads link
Linking GA4 and Google Ads lets each side use the other’s data: campaigns become visible in GA4 reports, and GA4 audiences and conversions become usable in Google Ads.
After linking, you have to decide where conversions are counted from. If the same action is counted both from GA4 and from the Google Ads tag directly, conversions appear twice and bidding runs on inflated data. I cover the detail on the GA4 link page.
Frequently skipped settings
Data retention defaults to a short window; without extending it you cannot analyse historical data. Filtering internal traffic also gets skipped — your own team’s visits contaminate the data.
The referral exclusion list is critical on sites using payment providers: a user returning from the payment page is counted as a new session, and the sale appears with its source lost.
How do we start? First I audit your existing setup: which events are measured, which are key events, whether anything is double-counted. I send the gaps in priority order in writing. You can reach me from the contact page.
Frequently Asked Questions
Did my Universal Analytics data move to GA4?
No, the two data models differ and there is no automatic migration. If you need the old data it has to have been exported separately; GA4 only shows data from its own installation date onwards.
Do I need Tag Manager for GA4?
Not strictly, but in practice it makes things much easier. Managing tags in one place means not touching the site for every change. I cover this on the Tag Manager setup page.
Why do GA4 and Google Ads conversion numbers differ?
The two systems use different attribution models and different time windows. Small differences are normal; large ones usually indicate double counting or missing tagging.