GA4 Key Events vs Conversions: What Changed and Why It Matters.

In March 2024, Google renamed "conversions" to "key events" inside GA4. On the surface it looked like a cosmetic change — a label swap, nothing more. In practice, the rename rippled through every report, every API query, every BigQuery export, and every conversation you have with a client who opens GA4 and immediately asks: "Where did my conversions go?"

The deeper issue is that the rename was trying to solve a real conceptual problem — the word "conversion" meant two different things in two different products, and Google wanted to separate them. That logic is sound. But because the rename only happened on the GA4 side, and Google Ads kept its own "conversion" language entirely intact, most practitioners ended up with more confusion, not less. This post explains what actually changed, what the real difference is between a GA4 key event and a Google Ads conversion, and exactly what you need to update in your own stack.

Why Google Renamed Conversions to Key Events

Before the rename, GA4 had one word — "conversion" — doing two distinct jobs:

• In GA4 Admin and reports: a flag on an event that says "this one matters." Checked a box next to purchase in GA4 → Events, and it became a conversion. That changed how it was reported: you'd see it in the Conversions report, it'd show up in the conversion column in User Acquisition, and so on.
• In Google Ads: a bidding signal. When you imported a GA4 conversion into Google Ads, it became a target that Smart Bidding algorithms actually optimized toward — allocating spend to maximize it.

These are different things. A business might want to mark video_play as important for analytics purposes without wanting Google's bidding algorithm to spend money getting people to play videos. The old model didn't cleanly separate those two decisions.

Google's solution: in GA4, the concept of "this event is important to us" is now called a key event. The concept of "this event tells Google Ads how to spend money" remains a conversion — but it now lives exclusively in Google Ads, not in GA4 Admin. You create key events in GA4. You create conversion actions in Google Ads by importing those key events. Two steps, two products, two clearly separate decisions.

That's the theory. Why it caused confusion in practice: the GA4 UI changed overnight, but the mental model didn't. Practitioners who had been calling them conversions for years opened GA4 and found the word gone. And for anyone who uses GA4 and Google Ads together, the import flow still says "Import from Google Analytics 4 conversions" on the Ads side — because Google Ads kept its own terminology entirely.

GA4 Key Events vs Google Ads Conversions — The Actual Difference

Here is the clean separation:

GA4 Key Event

• Defined inside GA4: Admin → Data display → Events → toggle "Mark as key event"
• Appears with special treatment in GA4 reports — its own Conversions report (now called Key Events), a dedicated column in acquisition and engagement reports
• Has no bidding implication on its own. GA4 knows nothing about how you're running campaigns
• You can have as many key events as you like, within reason (more on limits below)
• Historical data: marking an event as a key event applies retroactively — GA4 backfills up to 3 days

Google Ads Conversion

• Defined inside Google Ads: Goals → Conversions → New conversion action → Import → Google Analytics 4 → select your key event
• This is what Smart Bidding algorithms use. Target CPA, target ROAS, Maximize Conversions — all of these optimize toward Google Ads conversion actions, not GA4 key events
• Must be explicitly created per-event — having a key event in GA4 does not automatically make it a Google Ads conversion. You must import it
• Can be set as "Primary" (included in the bid strategy) or "Secondary" (tracked for observation only, not used for bidding)

The practical implication: a scroll event can be a GA4 key event for engagement tracking without ever becoming a Google Ads conversion. A purchase event should be both. These are two separate decisions, and now — after the rename — they're made in two separate places.

What Changed in GA4 After the March 2024 Rename

If you've been using GA4 for a while, here is a precise accounting of what moved:

UI changes

• GA4 Admin → Events: the "Mark as conversion" toggle is now "Mark as key event"
• GA4 Reports → Lifecycle: "Conversions" report renamed to "Key events"
• In User Acquisition, Traffic Acquisition, and Engagement reports: the "Conversions" column is now "Key events"
• Google Ads → Goals → Conversions → Import: still says "Import from Google Analytics 4 conversions" (Google Ads language is unchanged)

API and dimension changes

This is where technical teams need to act. The Data API dimension name changed:

• Old: conversion_event (also eventName filtered by isConversionEvent)
• New: key_event_name (also isKeyEvent as a filter dimension)
• The metric conversions is now keyEvents in the Data API

If you have scripts, dashboards, or scheduled reports querying the GA4 Data API using the old dimension or metric names, they will break or return empty results after this change. Audit every API consumer you have.

BigQuery export changes

In the raw BigQuery export, the event parameter is_conversion_event was renamed to is_key_event. Historical rows written before the rename still use is_conversion_event. Any BigQuery query that references this field across a multi-year date range needs a COALESCE or conditional expression to handle both column names — or it will silently miss everything before the cutover date.

New metric: sitewide key event rate

GA4 added a "Sitewide key event rate" metric alongside the rename — it reports the percentage of sessions that contained at least one key event. This exists in the Advertising workspace in GA4. It's a useful top-level health indicator and has no equivalent in the old conversion framework.

Common Mistakes After the Rename

Assuming key events automatically become Google Ads conversions

This is the most common mistake. You mark lead_form_submit as a key event in GA4 and expect it to start appearing in Google Ads reports and feeding Smart Bidding. It doesn't. You must go into Google Ads, create a new conversion action, choose "Import from Google Analytics 4," and explicitly select that key event. Until you do that step, the Google Ads campaign has no visibility into it.

A related variant: an account manager removes the old GA4 conversion action in Google Ads during a "cleanup" and doesn't know they need to re-import it under the new key events framework. Smart Bidding suddenly has no conversion data. Campaign performance tanks. No one can figure out why because both GA4 and GTM report everything as working.

Marking too many events as key events

GA4 allows up to 30 key events per property. That's a hard limit, not a soft suggestion. Beyond that, new toggles won't take effect. More practically, a property with 25 key events becomes analytically useless — every acquisition report shows 25 conversion columns, the "Conversions" total in summary cards is meaningless, and executives stop trusting the numbers because no one can explain what's being counted.

The right number is small — typically 5 to 10 events that represent genuinely distinct business outcomes. If you find yourself wanting to mark page_view or session_start as key events, those are engagement signals better tracked via custom dimensions or Explorations, not key events.

Broken BigQuery queries with no historical fallback

As noted above: if you have scheduled queries in BigQuery that filter on is_conversion_event = TRUE, those queries now return partial data. Rows after the rename use is_key_event; rows before it use is_conversion_event. A query that only handles the new column name will silently drop all pre-March-2024 history. The fix is:

• Use COALESCE(is_key_event, is_conversion_event) = TRUE for cross-historical queries
• Or partition your query at the rename date and union the results
• Add this as a standing check in any data pipeline that touches conversion data

Confusing primary vs secondary conversions in Google Ads

On the Google Ads side, the word "conversion" never went away — it applies to every imported GA4 key event. Within that, Google Ads further separates conversions into primary (used for bidding optimization) and secondary (tracked for reporting but not included in the bid strategy). A common mistake after the GA4 rename is importing a soft engagement event — like scroll or video_start — as a primary conversion, because it's technically available to import. Smart Bidding then optimizes toward scroll depth instead of purchases, and campaign performance craters while all the automated reports show "conversions up."

After any import of a new GA4 key event into Google Ads, immediately verify whether it was set as primary or secondary, and correct it if needed.

How to Set Up Key Events Correctly

Marking key events in GA4

1. Open GA4 → Admin → Data display → Events
2. Find the event you want to mark. Toggle "Mark as key event" to on
3. GA4 will backfill up to 3 days of historical data for the newly marked event
4. The event now appears in the Key events report and in conversion columns across standard reports

Events that typically should be key events: purchase, generate_lead, sign_up, begin_checkout (for funnel measurement), contact, book_appointment.

Events that should not be key events: page_view, session_start, first_visit, scroll, user_engagement. These are high-volume background events that will inflate conversion totals and make reports unreadable.

Importing GA4 key events into Google Ads

1. In Google Ads, go to Goals → Conversions → Summary
2. Click the blue "+" button → New conversion action
3. Choose "Import" → "Google Analytics 4 properties"
4. Select your GA4 property and the key event you want to import
5. Configure the conversion settings: value (fixed or dynamic), count (every or one-per-click), attribution model
6. After saving: confirm the newly created conversion action has the correct primary/secondary status

One important detail on attribution: the attribution model you choose here (data-driven, last click, etc.) is the Google Ads attribution model, which affects how the conversion credit is distributed across clicks in that campaign. It's independent of the attribution model in GA4 settings, which governs how GA4 reports attribute sessions to channels.

FAQ — GA4 Key Events and Conversions

What are GA4 key events?

A GA4 key event is an event you've flagged as important to your business inside GA4 Admin → Events. Flagging it changes how it appears in GA4 reports — it gets a dedicated Key Events report and appears in conversion columns across acquisition and engagement reports. It has no bidding implication in Google Ads unless you separately import it there as a conversion action.

Did Google remove conversions from GA4?

Google did not remove the concept — they renamed it. What used to be called a "conversion" inside GA4 is now called a "key event." The functionality is identical: you mark important events, they appear in dedicated reports. The word "conversion" in GA4 UI and API now refers only to events that have been imported into Google Ads. On the Google Ads side, nothing changed — conversions are still called conversions there.

What is the difference between a key event and a conversion in GA4?

Inside GA4 reports today, "key event" and "conversion" are the same underlying concept — an event marked as important. Google uses "key event" for the GA4-side flag and reserves "conversion" for the Google Ads concept. The meaningful distinction is: a key event is purely a reporting designation within GA4. A conversion (in Google Ads) is a key event you've imported into Google Ads and configured for bidding. Every Google Ads conversion started as a GA4 key event, but not every GA4 key event is or should be a Google Ads conversion.

How do I import GA4 key events into Google Ads?

In Google Ads: Goals → Conversions → New conversion action → Import → Google Analytics 4 properties → select your property → select the key event. The accounts must be linked (GA4 Admin → Product links → Google Ads links) before the import option appears. After importing, set the conversion as primary or secondary depending on whether you want it to influence Smart Bidding.

How many key events should I have in GA4?

GA4 enforces a hard limit of 30 key events per property. Practically, keep the number small — typically 5 to 10. Each key event adds a column to your acquisition and engagement reports; too many makes those reports unusable. Only mark events that represent a genuinely distinct business outcome: a purchase, a lead form submission, a sign-up, a booking. High-volume background events like page_view and scroll should not be key events.

Why does GA4 still say "conversions" in some places?

The rename was not applied uniformly. Some older views and features — particularly in the Advertising workspace and in some API responses — still use "conversions" language. The Admin → Events interface now clearly says "key events." Standard reports say "Key events." But the Google Ads linking flow and some of the Advertising workspace metrics still use legacy terminology. This is a known inconsistency that Google has been cleaning up incrementally. When in doubt, "key event" is GA4's internal concept; "conversion" belongs to Google Ads.

What is the key event rate in GA4?

The sitewide key event rate metric in GA4 reports the percentage of sessions that included at least one key event. It gives a quick health-check on whether your site's key actions are happening at a rate consistent with your goals. It lives in the Advertising workspace. You can break it down by traffic source, device, and page using Explorations. A sudden drop in key event rate with no corresponding change in traffic is a good early indicator that a key event tag broke or was paused.

Do GA4 key events affect Google Ads Smart Bidding?

Not directly. A GA4 key event only affects Smart Bidding after you import it into Google Ads as a conversion action and set it as a primary conversion. If you mark an event as a key event in GA4 but never import it into Google Ads, Smart Bidding has no knowledge of it. If you import it as a secondary conversion, Smart Bidding tracks it for observation but does not optimize toward it. Only primary conversion actions in Google Ads actively influence bid strategies.