Key events in GA4: choosing, marking and counting your conversions

A key event is an event you have told GA4 to treat as a goal: a purchase, a submitted lead form, a sign-up, a booked call. Google renamed "conversions" to "key events" in 2024 so that the word conversion could keep its meaning in Google Ads, where these same events arrive as conversion actions. Which events you pick, and how you count them, decides what every conversion rate, every attribution report and every Smart Bidding campaign optimises for. This article covers the choice, the switch, the counting method, the trick for events that do not exist yet, and the hand-off to Google Ads.

Part of the GA4 setup guide, step 8. You need events arriving in the property; if you have only just installed the tag, do that first.

Choose few, and choose outcomes

The best test for a key event: would the business be happy if this number went up on its own? A purchase, yes. A lead form submit, yes. A scroll to 90 percent, no. A page view of the contact page, no; that is a step, not an outcome. Most sites need two to four key events: the primary outcome (purchase or lead), a secondary one (newsletter sign-up, account creation, brochure download) and, for service businesses, a phone or WhatsApp click.

Keep steps as ordinary events. You can still see them in funnels and explorations; they just do not pollute conversion rates. A property with twelve key events tells you nothing, because every report that says "key events" adds them all together.

Mark an existing event as a key event

Go to Admin › Data display › Events. The table lists every event name GA4 has received in the last 30 days. Find the one you want and switch on Mark as key event in the last column. From that moment, new occurrences count; past ones are not re-labelled.

Then open Admin › Data display › Key events. The event appears there with its counting method and a network settings column for Google Ads. The event needs to have arrived at least once before it shows up in the Events table; for one that has not, see the next section.

Create a key event before the event exists

Under Key events › New key event, type the event name exactly as your Tag Manager tag will send it (generate_lead, sign_up, purchase). GA4 registers it as a key event straight away and starts counting as soon as the first one arrives. This is the way to do it when you set up tracking and key events on the same day.

Prefer Google's recommended names where one fits: purchase, generate_lead, sign_up, login, add_to_cart, begin_checkout. They unlock the standard reports and Google Ads recognises them when you import. Use a custom name only for something the list does not cover, and keep it snake_case and lowercase.

Set the counting method

Open a key event's menu (the three dots in the Key events table) and choose Change counting method. Two options:

• Once per event (default): every occurrence counts. Right for purchases, where two orders in one session are two orders.
• Once per session: a visitor who triggers the event three times in a session counts once. Right for leads, sign-ups and downloads, where repeats are the same intent.

Mismatched counting is the usual reason a lead count in GA4 is higher than the number of emails in the inbox: a form that lets people submit twice, counted once per event.

Create an event from another event

Sometimes the event you want to mark is a special case of one you already have: a page_view of the thank-you page, a file_download of the price list, a click on the phone number. Under Admin › Data display › Events › Create event you define a new event from conditions on an existing one, for example event_name equals page_view and page_location contains /thank-you, and name it generate_lead. Then mark the new event as a key event.

It works for simple cases and saves a Tag Manager change. The limits: conditions only match parameters that already arrive, the new event only exists from creation onwards, and the thank-you-page method counts a page reload as a second lead. For anything that matters, a Tag Manager trigger on the form tool's own success event is the better source.

Give the event the parameters you will want later

A key event with no parameters is a count. A key event with value, currency and a descriptive parameter (form_name, plan, lead_type) becomes a report. Send value on leads too, with an average deal value, so Google Ads can bid on value rather than count. Send currency alongside it or the value is dropped. Register the descriptive parameters as custom dimensions under Admin › Data display › Custom definitions, or they will not appear in reports (Measurebase's audit tells you when a parameter arrives that is not registered).

Import the key events into Google Ads

With the Ads account linked (Admin › Product links), go to Google Ads › Goals › Conversions › New conversion action › Import › Google Analytics 4 properties and tick the key events you want to bid on. For each, set the same counting (one for purchases, "one per click" for leads), a value, and the attribution model; Ads uses its own click-based attribution, so the daily numbers never match GA4 exactly, but they should move together.

Import only the primary outcomes as primary conversion actions. Secondary ones can be imported as "secondary" so they are observed but do not drive bidding.

Check them: DebugView, Realtime and the next day

Trigger each key event yourself. In DebugView the event shows with its parameters, and the key event badge appears next to its name. In Realtime the "Key events by event name" card updates within seconds. The next day, Reports › Engagement › Key events shows the count by source, and the Advertising workspace shows attribution paths. If a key event shows in DebugView but never in the reports, the usual cause is a parameter that fails validation (a non-numeric value, a missing currency).

When you run GA4 through a server container

Key events are defined in the GA4 property, so nothing here changes with server-side tagging. What changes is how many of them arrive. Browser-only GA4 loses the conversions of visitors with ad blockers and, on Safari, part of the returning-visitor attribution after the 7-day cookie cap. Routed through a server container on your own domain, those hits are no longer filtered and the cookie lives longer, so key event counts rise and attribution gets more complete, without a single setting changing in this article. The one thing to add on the server side is deduplication when the same conversion is also sent server-to-server, for which the event ID matters; the e-commerce guide covers it for purchases.

Frequently asked questions

How many key events can a property have?

Thirty on a standard property, fifty on GA4 360. You will not need the limit; two to four is the healthy range.

Can I unmark a key event and keep the data?

Yes. Unmarking stops counting it as a key event from that moment; the events themselves stay in the property and the historical key event counts remain in past reports.

Why is my key event count different from the number of form submissions?

Three usual causes: counting method set to once per event on a form that can be submitted twice, a thank-you-page event that counts reloads, or consent (visitors who declined analytics never send the event). Check DebugView for a real submission and compare the parameters.

Do key events need a value?

No, but value makes them far more useful: Google Ads can optimise for value, and GA4 shows revenue-like totals for leads. Use an average deal value for leads and the real amount for purchases, always with a currency.

What happened to conversions in GA4?

They were renamed key events in March 2024. In Google Ads, the imported ones are still called conversions. Same thing, two names, chosen so each tool's vocabulary stays consistent.

Should I mark purchase as a key event or is it automatic?

It is marked automatically once a purchase event arrives, as are a few app events. Check the Key events table anyway; it is the only event GA4 marks for you.