Key event

A key event is an action in Google Analytics 4 that you have marked as one of the things you actually care about. A form sent, an order placed, a booking started. Everything a visitor does is recorded as an event; a key event is an event you have promoted, and the promotion is what makes the reporting worth reading.

In short

• An event you have marked as mattering to the business.
• The new name for what GA4 called conversions until 2024.
• Google Ads still says conversions, and its totals will differ.
• Mark a few things, not everything.

The rename, and what it does not mean

If you learned analytics before 2024 you learned to call these conversions. Google changed the word in Google Analytics 4 that year, and a great deal of published material still uses the old one.

Nothing about the measurement changed. A key event is the same object under a new label. What changed is that Google Ads kept the word conversion for its own counting, which was the point of the exercise: two systems were producing different totals for the same underlying purchases, both were correct by their own rules, and sharing a word made that look like a fault.

So the vocabulary now tells you which system is speaking. Key event means analytics. Conversion means advertising.

Why the two will never agree

Businesses lose real time trying to reconcile these figures, so it is worth understanding why the effort is wasted. Google Analytics 4 counts the action on the day it occurred, and attributes it using its own model. Google Ads counts the same action against the date of the advert click that preceded it, which may be days earlier, and only within its conversion window. It also includes modelled figures to account for people it cannot observe individually, which analytics does not do in the same way.

Two systems, two clocks, two rulebooks. A gap between them is the expected outcome rather than evidence of a broken setup. Use each for the question it answers: Google Ads to decide about campaigns, analytics to understand behaviour across every channel including the ones you do not pay for.

There is a second consequence of the split that costs more than the mismatched totals. Marking something as a key event in analytics does not create anything in Google Ads. The action has to be imported there as a conversion action, and it arrives marked secondary, which means bidding ignores it until somebody promotes it to primary. Plenty of accounts run for months in that state, correctly configured on the analytics side and optimising towards nothing on the other.

Choosing what to mark

This is the decision that determines whether any of it is useful, and the common error is generosity.

Every additional key event dilutes the total, and GA4 caps you at thirty per property anyway, which is a hint about the intended spirit. The failure mode of counting everything is set out on the conversion rate entry. What matters at this end is the decision itself, because the toggle is where it gets made.

The discipline is to ask what you would change if the number moved. An inquiry form sent is a real answer. A video play is not, for most businesses, and if it genuinely is then it should be the one you mark rather than one of six.

• A service business. Contact form submitted. Possibly a booking started.
• A shop. Purchase. Possibly add to cart, and only because it explains where purchases are being lost.
• Anybody at all. Whatever the website exists to produce, stated in one sentence.

The prerequisite everybody skips

Marking an event as key does nothing if the event itself is unreliable, and a surprising number are. Form submissions that only register when a particular confirmation loads. Buttons that fire the event twice. Tracking that stops working after a site update and is noticed months later because nobody looks at a number they trust. In each case the key event faithfully reports something wrong.

Before marking anything, submit your own form and confirm the event appears where it should. Then repeat that after any change to the site, because the most common cause of a sudden drop is not a marketing problem at all. The wider setup this depends on is the whole of tracking.

Words you will hear

• Event. Anything a visitor does that is recorded. Key events are a subset.
• Conversion. The same idea in Google Ads, and the old GA4 word.
• Conversion window. How long after an advert click Google Ads will credit the campaign.
• Modelling. Filling in where individuals cannot be observed. Both tools do it, by different methods and at different points, which is part of why the totals differ.
• Attribution. How credit is divided between the touchpoints that preceded the action, which is why tagging links with UTM parameters matters upstream of this.
• Thank you page. The page shown after a form is sent, and a common stand-in for the event itself.

The test

Ask somebody in your business what the website is for, in one sentence. If they can answer, you have found your key event. If they cannot, no amount of configuration will help, and that conversation is the piece of work to do first.

Everything after it, including the conversion rate that gets calculated from it, depends on somebody having decided what counts.