Quick answer: In March 2024 Google split the old GA4 "conversion" concept into two things. Key events are now GA4's term for the events you mark as important for reporting and analysis. Conversions is now exclusively a Google Ads term, used for bidding. The two are linked but not identical. Most audits we run still treat them as a single concept — and that's where the bidding and reporting numbers start to diverge.
This post explains the new model, the audit checks for each side, and the four configuration mistakes we see most often.
What changed in March 2024
Before March 2024, GA4 had a single concept called "conversions." You marked an event as a conversion, and that flag did two things at once:
- The event appeared in GA4's Conversions report and was counted in conversion-related metrics like conversion rate.
- The event was eligible for export to Google Ads for bidding.
In March 2024, Google split these two concepts:
- Key events — the GA4-side flag. Marks an event as important for analysis. Affects GA4's reporting (Engagement → Key events report, conversion-rate metrics, audience definitions).
- Conversions — now only a Google Ads concept. A conversion in Google Ads is imported from GA4 key events, and the import is configured on the Ads side. Bidding strategies use conversion data on the Ads side.
The unfortunate part of the renaming: GA4's own reporting still shows the legacy column header "Conversions" in some places (for now), and the Google Ads UI still uses the word "Conversion" for what is, in the GA4 source, a key event. So you have to be careful which interface you're looking at when you read a number.
The new mental model
Think of it as two flags that travel together:
| Question | Which flag | Set where |
|---|---|---|
| Should this event count for GA4 conversion-rate, engagement reports, audience criteria? | Key event | GA4: Admin → Events → Mark as key event |
| Should Google Ads bid on this event? | Conversion (Ads import) | Google Ads: Tools → Conversions → Import from GA4 |
You usually want both flags for high-value events (purchase, lead-form submit, signup). Sometimes you want only the GA4 key event flag (a soft engagement event you analyze internally but don't bid on). Almost never do you want the Google Ads side without the GA4 side — that means the bidding signal isn't visible in your analytics.
The 5-step audit
Step 1: List your current key events
In GA4: Admin → Events. The right-hand column shows a toggle for "Mark as key event." Note every event with the toggle on. There should be 3–10 of them for most businesses. If you have more than 15, you're probably marking engagement events as key events, which dilutes conversion-rate metrics.
Step 2: Verify each is firing
For each key event, go to Reports → Engagement → Events and check the 7-day count. Any key event with 0 events in 7 days is broken — usually a tag issue, a renamed event, or a parameter mismatch. This is the most common finding.
Step 3: Cross-check against Google Ads
In Google Ads: Tools → Conversions. The "Source" column should show "Google Analytics 4 properties" for imported conversions. Verify that every event you bid on in Ads matches a GA4 key event of the same name. A common mistake: bidding on Sign up in Ads while GA4 has the event as signup (no space). The import will silently fail to populate.
Step 4: Check the conversion-counting setting
For each Ads conversion, check Count: One (one conversion per click — for leads and signups) or Every (every conversion per click — for purchases). The wrong setting inflates or deflates bidding signals. For ecommerce purchases, always use Every; for lead forms, almost always One.
Step 5: Verify conversion value
Bidding strategies that optimize for ROAS or value require a non-zero value parameter on the event. For purchase, this is automatic if your ecommerce data layer is correct. For leads, you need to assign a value in the Ads conversion settings (e.g., $50 per qualified lead). Missing value → bidding falls back to "more conversions" instead of "more value." This is a frequent cause of inefficient Ads spend.
4 mistakes we see most often
1. Marking page_view as a key event
This is the #1 mistake — and the pillar checklist's item #12 calls it out for a reason. Marking page_view (or a specific page_view filtered by URL) as a key event turns every page view into a "conversion," which destroys conversion-rate metrics and floods Google Ads with junk signal. If you want to track key page visits, use a custom event with a meaningful name like view_pricing_page, not page_view.
2. Old "conversion" events still active after the rename
If you set up conversions before March 2024 and haven't reviewed them since, you might have events flagged as both legacy conversions and new key events. They're not duplicated in reports — but it's worth opening each one and confirming the flag is set to "Mark as key event" so the new terminology applies cleanly.
3. Same event imported into Google Ads twice
If you previously had a Google Ads conversion tag on the site (the legacy AW-XXXXXX/conversion pixel) and you also import the same conversion from GA4, you're double-counting in Ads. Symptom: Ads conversion count is consistently ~2× the GA4 key-event count. Solution: turn off one of them. Importing from GA4 is generally the cleaner approach.
4. Currency mismatch on multi-region accounts
If your GA4 property reports in USD but you ship to Europe and the event sends currency: EUR, the value gets stored as EUR in GA4 but the Ads bidding engine assumes the property currency. ROAS bidding then optimizes for the wrong number. Always send the actual transaction currency, and make sure your GA4 property currency matches your most-common transaction currency.
When Google Ads conversions and GA4 key events don't match
It's normal for the two counts to differ — but the size of the gap tells you whether something's broken. Some typical patterns:
- Ads is 10–20% lower than GA4: normal. Ads uses last-click attribution and a different conversion window. GA4 uses data-driven attribution by default. The two systems were never going to agree exactly.
- Ads is 50%+ lower than GA4: the import is failing — wrong event name, missing currency, conversion-counting set to "One" when it should be "Every," or stale tag.
- Ads is higher than GA4: double-counting (legacy pixel + GA4 import both firing), or the Ads conversion is firing on a different event than the GA4 key event.
We have a dedicated post on this discrepancy: GA4 vs Google Ads conversion mismatch.
Frequently asked questions
Are "key events" and "conversions" the same thing in GA4?
In GA4's reporting interface they refer to the same underlying flag — the rename in March 2024 was largely cosmetic on the GA4 side. The functional split is: "key event" is the flag in GA4 admin, "conversion" is the term used by Google Ads when it imports that flag for bidding.
Do I need to re-mark all my old conversions as key events?
No. Events already marked as conversions before the rename were automatically migrated to "key events." But it's worth reviewing the list to confirm the flag is set correctly and the events are still firing.
Can I have a key event in GA4 that isn't a Google Ads conversion?
Yes — and you often should. Soft engagement events (scroll-to-bottom, video-50%, FAQ-expand) can be useful as key events for GA4 analysis without being valuable as bidding signals. Mark them as key events in GA4 but don't import them into Google Ads.
What about Microsoft Ads / Meta Ads imports?
Those platforms use their own conversion-tracking pixels, not GA4 key events. The rename doesn't affect them. If you bid in Microsoft Ads or Meta, set up native conversion tracking on each platform; don't rely on GA4 key events to flow through.
Does Consent Mode v2 affect key event counting?
Yes — if a user has denied analytics_storage, the event is modeled rather than measured. Modeled events count in GA4 key-event totals (with a small lag) but may not export to Google Ads at the user level. See our Consent Mode v2 checklist for the implementation details.
Can I un-mark a key event later?
Yes. Open the event in Admin → Events and toggle off "Mark as key event." Historical data is unaffected; future events still fire but no longer count toward key-event metrics. The associated Google Ads import will continue counting until you also remove it on the Ads side.
Audit key events and Ads imports automatically
A Snifflytics audit checks that each key event is firing, that no engagement event (like page_view) is marked as a key event, and that values and currencies are set correctly for bidding. Run it alongside the full 25-point GA4 audit checklist. Start a free audit.