Google Analytics 4 measures some events automatically as soon as it's installed (page views, scroll, clicks on outbound links, file downloads), but the part that really separates a useful analytics setup from a generic one is custom events: specific actions relevant to your particular business, which Google can't guess on its own because they depend on exactly how your site or product works.
What a custom event is, with concrete examples
If you run an online store, it could be "add to cart", "start checkout" or "apply a discount code". If you run a services site, it could be "click to call", "contact form submission" or "watching an explainer video to the end". If you run a content site or blog, it could be "click on an affiliate link" or "newsletter sign-up" from a specific article. Each of these events captures an intent far closer to real business value than a simple page view.
Why visits alone say so little
Two websites can have exactly the same monthly visit count and radically different business results, if one converts that traffic into calls, forms or sales and the other doesn't. Measuring only visits is like counting how many people walk into a physical shop without noticing how many of them actually buy something: it's a starting figure, not a measure of success.
How to decide which custom events to set up first
The reference question is: if I had to pick just three actions on my site that prove a visitor is genuinely interested in what I offer, what would they be? Those three actions are the first ones to set up as events, before trying to measure absolutely everything that happens on the site, which tends to generate more data noise than useful information.
The step almost nobody takes: marking events as conversions
Setting up an event in GA4 isn't enough if it isn't also marked as a conversion (or "key event", in Google's current terminology), because only then does it show up prominently in business-outcome-focused reports, and only then can it be used as an optimisation goal in Google Ads campaigns linked to the same analytics account.
Frequently asked questions
Do I need technical skills to set up custom events?
For the simplest cases, Google Tag Manager lets you configure many events with no code, just by defining which click or action should trigger the event. For more complex cases (actions inside an app, for instance) some occasional technical support may be needed.
How many custom events is too many?
There's no strict technical limit, but from a practical standpoint, more than ten or fifteen custom events tends to produce reports that are hard to interpret. It's better to prioritise the ones that genuinely matter than to try measuring absolutely everything.
Do custom events replace GA4's automatic metrics?
No, they complement each other: automatic metrics give general context (how much traffic, where it comes from, how long people stay), while custom events add the layer of what genuinely valuable actions that traffic is taking.