Most GA4 setups we inherit are installed and untouched. Data flows in, nobody trusts it, and the reports get opened once a quarter to confirm a suspicion.
Here's the minimum that makes it useful.
1. Mark the right events as key events
GA4 collects events automatically, but nothing is a "key event" (what used to be called a conversion) until you say so. Mark only what represents money: form submit, purchase, WhatsApp click, call click.
Do not mark page views or scroll depth. Once everything is a conversion, nothing is.
2. Filter out your own traffic
Your team refreshing the site is a meaningful share of sessions on a small site. Set up internal traffic filters by IP and switch them to active — creating the filter isn't enough, and that's the step people miss.
3. Turn on cross-domain tracking if you need it
If your checkout, booking tool or payment page sits on a different domain, GA4 will treat the same person as two users and credit the sale to a referral from your own site. Configure the domains explicitly.
4. Set data retention to 14 months
The default is 2 months. That means no year-on-year comparison, ever. It's one dropdown in admin settings and it's the single most common regret.
5. Link Google Ads and Search Console
Without the Ads link, you can't see which campaigns produced which behaviour. Without Search Console, organic queries stay invisible inside GA4.
6. Set up UTM discipline
GA4 can only report what your links tell it. Agree a convention — lowercase, consistent source and medium values — and use it everywhere. facebook and Facebook become two different sources and nobody notices for months.
7. Build three reports and ignore the rest
- Key events by session source — what actually produces results.
- Landing page performance — where paid traffic arrives and whether it converts.
- Core Web Vitals via the Search Console link — speed on real devices.
8. Send server-side events too
Browser-only tracking loses a meaningful share of events to blockers and browser restrictions. Server-side measurement recovers much of it.
GA4 is not a source of truth about revenue. Your bank account is. GA4 is for understanding behaviour between the click and the sale.
What to leave out of a GA4 setup
- GA4 not matching platform numbers. It never will — different windows, different models. Here's why.
- Bounce rate. GA4 measures engagement instead, and it's more useful.
- Exploring every report. Most exist for enterprises with dedicated analysts.
To see how much the platforms are over-claiming on your account, use the blended ROAS and MER calculator.
Questions people ask
What is the minimum GA4 setup worth doing?
Mark the right events as key events, filter out your own traffic, set data retention to 14 months, link Google Ads and Search Console, and keep UTM tagging consistent. Those five take an afternoon and cover most of what a small business needs.
Why does GA4 show different numbers from my ad platform?
They measure different events, at different moments, under different attribution rules, and GA4 samples large datasets. The gap is expected. Use each for what it is good at rather than trying to reconcile them.
Does data retention really need changing?
Yes. GA4 defaults to a short retention window, so year-on-year comparison quietly becomes impossible. Setting it to 14 months is a single toggle and it cannot be applied retrospectively, which is why it is worth doing on day one.
Should I filter my own traffic?
Always. On a low-traffic site, the team’s own visits can be a noticeable share of sessions and will distort every conversion rate you look at.
Want this set up once, properly? Tell us what you're running.