Key event counting changes
GA4 renamed 'conversions' to 'key events' and added a counting-method choice: count a key event once per event, or once per session. The same traffic yields different totals under the two methods, and the rename plus the Ads-side split (conversions stay an Ads concept) confuse reconciliation. This page explains the counting methods and why totals move when they change.
From conversions to key events
GA4 now calls the events you care about 'key events' in Analytics, while 'conversions' became the term used on the Google Ads side. The rename is not cosmetic for reconciliation: the same underlying event can be reported as a key event in GA4 and as a conversion in Ads, and the two surfaces can count it differently.
Per-event vs per-session counting
Each key event can be counted with one of two methods. 'Once per event' increments the total every time the event fires, so a user who submits a form twice in a visit counts twice. 'Once per session' counts the key event at most once per session, regardless of how many times it fires. Switching methods changes the conversion total for identical traffic.
When a conversion total steps up or down on a specific date with no campaign change, check whether the counting method was changed or whether an event was newly marked (or unmarked) as a key event.
- Conversions renamed to key events in GA4
- Counting method: once per event or once per session
- Per-event double-counts repeated actions in a visit
- Marking/unmarking an event as key shifts totals too
How it appears in analytics and logs
A conversion total that changed on a fixed date with steady traffic usually reflects a counting-method switch (per-event vs per-session) or the key-event rename, not demand.
Diagnostic use case
Explain why a conversion total dropped or rose after switching a key event's counting method, or after the conversions-to-key-events rename.
What WebmasterID can help detect
WebmasterID counts conversion events first-party with an explicit definition, so you can reconcile per-event versus per-session intent without a hidden default flipping totals.
Common mistakes
- Comparing conversion totals across a counting-method change.
- Assuming GA4 key events and Ads conversions count identically.
- Ignoring that marking an event as key changes historical comparisons.
Privacy and accuracy notes
Key-event counts are event aggregates, not identity. This page is educational, not legal advice on consent or measurement.
Related pages
- Engaged session edge cases
GA4's engaged session is the basis for engagement rate and the inverse bounce rate. A session counts as engaged if it lasts longer than the engagement-time threshold (default 10 seconds), records a key event, or has at least two pageviews/screenviews. The edge cases — fast single-view satisfactions, a changed threshold, background time — quietly move engagement and bounce numbers. This page documents them.
- Ads vs analytics discrepancies
It is normal for Google Ads and GA4 to report different conversion and click numbers for the same campaign. They use different attribution models, count conversions at different times (Ads at click time, GA4 at conversion time), define a click versus a session differently, and apply different windows and de-duplication. This page enumerates the documented reasons the two tools diverge.
- Duplicate transactions in ecommerce data
Duplicate transactions occur when one purchase is counted more than once — usually because the order-confirmation page is reloaded, bookmarked, or shared, or because a retry resends the same event. GA4 deduplicates ecommerce purchases on `transaction_id`, so an absent or unstable ID is the root cause. This page covers detection and the deduplication key.
- Event Explorer
Inspect key-event firing per session.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.