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Wrong key events: when GA4 conversions aren't outcomes

Marking page_view or scroll as key events, or sending purchase with no value or currency, turns conversion rates and ROAS into meaningless numbers.

GA4 mistakes · 10 Published

Step 1 of 5 In the property's event list, four events are marked as key events.

In 2024, GA4 renamed “conversions” to key events. The idea is the same: the events that represent an important outcome for the business, on which conversion rates, attribution and through the Google Ads integration, much of campaign optimisation are calculated. That is why marking the wrong event as key has consequences well beyond a report.

What wrong key events look like in GA4

In Admin → Events, the key event list includes things like page_view, scroll or click, next to real outcomes such as generate_lead or purchase. On top of that, purchase arrives with no value or currency. The consequences:

  • Conversion rates close to 100%, because almost every session has a page_view.
  • Attribution spread across interactions that aren’t outcomes.
  • ROAS and conversion value wrong or empty, because the purchase carries no amount.
  • If key events are imported into Google Ads, automated bidding optimises towards those interactions.

Why non-outcomes end up as key events

  • Events are marked “just in case”, to see more data in the conversion reports.
  • Old goals were migrated without checking whether they still made sense.
  • The purchase event was implemented without value parameters, or with value as text (covered in detail in the post about the purchase event).

How to audit your GA4 key events

  1. Go through the key event list and ask of each one: does it represent a business outcome?
  2. Compare the session conversion rate with reality: very high values usually mean an interaction event is marked as key.
  3. In DebugView, open a test purchase and check that it carries a numeric value and a currency.
  4. In Google Ads, review which conversions are imported from GA4 and which are primary.

How to define key events that are outcomes

  • Keep only outcomes as key events: purchases, qualified leads, sign-ups, quote requests. Intermediate interactions can still be measured as normal events.
  • Complete purchase with value (a number) and currency (an ISO 4217 code).
  • If an interaction matters for analysis, such as a click on the phone number, decide whether it is a real outcome or a metric of interest; only in the first case should it be key.
  • Review which conversions are primary in Google Ads, so bidding optimises towards real outcomes.

Google’s documentation: About key events.

How to check conversion rates make sense again

  • The conversion rate should drop to a level consistent with the business.
  • Test purchases should show revenue in the key event reports.
  • The change doesn’t alter data already processed: note the date so period comparisons stay correct.