GA4 Key Events: Marking the Actions That Matter

This guide uses Analytics Help: About key events, Conversions vs. key events in Google Analytics, Mark events as key events, Create or modify key events, Change the counting method of key events, Tutorial: Set up a key event and Create Google Ads conversions based on Google Analytics key events. Quotes are from those pages.

What a key event is

Google Analytics 4 records everything as events: page views, scrolls, clicks, form submissions. Google defines a key event as "an event that measures an action that's particularly important to the success of your business". Any event you collect can become one. You create or find the event that measures the action, then mark it as a key event, and from then on GA4 counts it separately in its reports.

For a service business that usually means a confirmed enquiry, a booking or a call click. For a shop it means purchases. If you have not set up GA4 yet, start with our GA4 basics guide.

Key events vs. conversions

GA4 used to call these actions conversions. Google renamed them because Analytics conversions and Google Ads conversions were measured differently, which led to discrepancies between the two tools. Google's page on the change now uses two words:

• Key event: an important action measured in Analytics, used to study traffic, behaviour and site journeys.
• Conversion: in Google's words, "an important action that you want to use to measure the performance of your ad campaigns and optimize your bidding strategy".

The path Google describes is Event, then Key event, then Conversion: you mark an important event as a key event, and if you want to bid on it in Google Ads, you create a conversion from it. Your older GA4 conversion data was not lost. Google says: "You can also continue to access your historical conversion data as key event data", so year-over-year comparisons still work.

Choosing the event to mark

The event has to measure the action itself. Google's own example is a confirmation page: the page_view event tells you someone landed on it, but "you can't mark that event as a key event since all pageviews will then count as key events." Instead, GA4 lets you create a new event from an existing one, without changing your site code.

Google's tutorial does this with the generate_lead event: in Admin, under Data display, click Events, then + Create event, name it generate_lead, choose to create it without code, base it on page_view and add a condition for the thank-you page URL. Google recommends using its recommended events such as generate_lead "whenever possible, instead of custom events", so you get the features built around them.

Two cautions from the same pages. A new event is not the same as a modified one: "Modifications overwrite existing events", so editing page_view itself would break your page view data. And make sure the event fires only when the action really happened, such as a form your site has accepted, not a click on the submit button. Our DebugView guide shows how to watch events arrive while you test.

Marking an event as a key event

If GA4 has already received the event:

1. In Admin, under Data display, click Events.
2. Find the event in the Recent events tab.
3. Click the star next to it.

For an event GA4 has not seen yet, click + Create event, enter its exact name and switch on Mark as key event. You then choose a default key event value and a counting method, and click Create. Google notes that special characters can't be used in the name, and that you can mark new events ahead of time so they are treated as key events once they arrive.

Google's page asks for the Marketer role or above on the property (one of its notes says Editor for marking an existing event). Marking takes effect from that moment: "It doesn't change historic data." Google says to allow up to 24 hours for a new key event to show in standard reports, while "Realtime reports update a few minutes after a user triggers a key event."

To stop, remove the star in the Key events tab. Google says turning off a key event "doesn't affect the data you've already collected; past events still show in reports as key events."

Limits and default key events

Google's limit is 30 key events for a standard property and 50 for an Analytics 360 property. Some events are marked by default on top of that: purchase on web and app, and on apps first_open, in_app_purchase, app_store_subscription_convert and app_store_subscription_renew.

If you link a Google Ads account and enable Ads Personalization, GA4 also marks add_to_cart, add_to_wishlist, begin_checkout, session_start, view_item, view_item_list and view_search_results as key events. If those suddenly appear in a lead-generation property, that link is the likely reason. For shop events and their parameters, see our GA4 ecommerce tracking guide.

Counting method

The counting method decides what happens when someone triggers the same key event more than once in a session. Google offers two options:

• Once per event (Recommended): every trigger counts. Five triggers in a session give five key events.
• Once per session (Legacy): the key event counts once in that session, however often it fires.

Once per session is the default for key events that came from Universal Analytics goals, either in an automatically created property or through the goals migration tool after April 2023. Every other key event defaults to once per event.

To change it, open the Key events tab under Admin, Data display, Events, use the menu at the end of the row, and pick Change counting method. Google notes: "Any changes to the counting method apply to future key events only, and won't apply to a key event's past data." So note the date in your reports if you change it.

Key event value

A key event can carry a money value. There are two ways, both on Google's Create or modify key events page:

• Send value and currency parameters with the event. The value must be a number, and the currency must be an ISO 4217 code such as USD. Google warns that if a parameter "is missing or invalid, the event is recorded with the correct count, but it won't be sent to Google Ads."
• Set a default value: in the Key events tab, open the row menu, click Set default key event value, enter it and save.

Use a value only if you have a sensible number to put on the action. The Event count by Event name card in the Realtime report lists the parameters received in the last 30 minutes, so you can check that value and currency arrive.

Where key events appear

Many standard reports, such as Landing pages and User acquisition, have a Key events column. It counts all key events by default; open the menu above the column to pick one key event. In explorations you can use metrics such as Key events and Session key event rate (see our explorations guide).

In the Advertising section, the attribution and path reports share out credit for key events between the channels that led to them. How that credit is split depends on the attribution model and lookback window, which our GA4 attribution guide covers. For what to put in a monthly report, see our website report guide.

Google adds that Google Ads conversions "don't appear in standard Google Analytics reports in the Reports or Explore sections of the product." They appear in the Advertising section, for example in the Conversion performance report.

Using key events in Google Ads

To bid on a key event, you create a Google Ads conversion from it. Google lists three requirements: link Google Analytics and Google Ads, enable auto-tagging in Google Ads, and be an administrator or editor of the property. Then, in Advertising, under Tools, open Conversion management, click New conversion, choose the Ads account and the key events, and save.

For each key event you can create one web and one app conversion in each linked Ads account. When the account already has goals from Analytics, Google Ads marks the new ones as secondary "to prevent counting the same event twice for bidding". Goal category and action optimization can only be changed in Google Ads.

Expect key events and conversions to differ. Google lists different attribution settings, lookback and conversion windows, counting methods and modelling among the reasons. Our Google Ads conversion tracking guide covers the Ads side, including the Google tag as an alternative to importing, and our auto-tagging guide covers the click ID that ties a visit to the ad.

A short checklist

This is our suggestion, based on the Google pages above:

1. Write down the two to five actions that matter for your business, and keep the list short.
2. Use one event per action, firing only on success (a thank-you page or a confirmed form submission), and prefer Google's recommended names such as generate_lead.
3. Mark each one with the star and test it in Realtime and DebugView with a real submission.
4. Check the counting method, especially on key events migrated from Universal Analytics.
5. Add a value only if you have a real figure, and confirm value and currency arrive.
6. Note the date of every change, because marking and counting changes only apply going forward.

Frequently asked questions

Are key events the same as conversions?

Not any more. Key events are the important actions you mark in Google Analytics. Conversions are the actions used to measure and bid on Google Ads campaigns, and you can create one from a key event.

How many key events can a GA4 property have?

Google's limit is 30 for a standard property and 50 for Analytics 360. Default key events such as purchase are marked in addition to that number.

Does marking an event as a key event change past data?

No. Google says it affects reports from the time you mark it and does not change historic data. New key events can take up to 24 hours to show in standard reports.

Should I count key events once per event or once per session?

Google recommends once per event, because it reflects what users actually did. Once per session is the legacy option and the default for key events migrated from Universal Analytics goals.

Why don't my GA4 key events match my Google Ads conversions?

They are measured for different purposes, and can use different attribution models, windows and counting methods. Google Ads conversions are reported in Google Ads and in the Advertising section of GA4, not in the standard reports.

Key events are only as good as the site events behind them: forms that report success, thank-you pages and clean tags. That is part of our website development work. See all our services, or email [email protected].