Short answer: A GA4 key event is an event marked as important in Analytics. A Google Ads conversion is an action Ads counts and, if primary, bids on. A key event turns into one only when imported. On 5 Nov 2026, 305 of the 886 Google Ads sites in our 1,727-site study (34.4%) listed 10 or more key events, and 42 (4.7%) marked a page view type event as key.

What is the difference?

GA4 key event Google Ads conversion

Used for Reporting, audiences Reporting and, if primary, bidding

Created by Marking an event as key Ads tag, GA4 import, offline import

Cost of junk Messy reports Bids tuned to the wrong action

GA4 "conversions" became "key events" in March 2024. A signup sent by an Ads tag and imported from GA4 counts twice.

What do sites mark as key events?

On 5 Nov 2026 we read the Google tags of 1,727 sites (1,201 B2B SaaS, 271 agencies, 255 ecommerce). GA4 writes its key event list into that tag.…