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GA4 renamed Conversions to Key Events in late 2024. The name change matters less than what most owners get wrong: marking too many things as Key Events, which destroys Smart Bidding and inflates every report.
Who this is forOwners who have GA4 installed but haven't yet defined which events count as real business outcomes. Or owners who marked everything as a Key Event and now have conversion reports that look like noise.
What you'll need
Step 1
GA4 has three event tiers: automatically collected, Enhanced Measurement, and custom. Only some can become Key Events. Pick the right tier for each business outcome.
Automatically collected events (page_view, session_start, first_visit) fire without configuration. You can't disable them and you shouldn't mark them as Key Events.
Enhanced Measurement events fire when Enhanced Measurement is enabled on the stream (Admin → Data Streams → Web → gear icon next to Enhanced Measurement). Includes scroll, click (outbound), file_download, video_start/progress/complete, view_search_results.
Recommended events are GA4's reserved-name events you fire manually: purchase, add_to_cart, view_item, generate_lead, sign_up, login, share. Use these names exactly when you fire custom events — Smart Bidding and reports recognize them.
Custom events are anything you name yourself (e.g., booking_completed, demo_requested). They work, but you lose the special handling that recommended events get in reports.
Rule: always prefer a recommended event over a custom one. Use generate_lead for any lead-gen action, sign_up for any account creation, purchase for any payment. Reserve custom events for things that genuinely don't fit a recommended name.
Step 2
Pick 2-4 events that represent real business outcomes. Resist the urge to mark more. Smart Bidding works best on a small set of high-value events.
For ecommerce: purchase is your primary Key Event. begin_checkout is a useful secondary (track checkout abandonment).
For lead-gen / B2B: generate_lead (or your custom lead event) is primary. sign_up is secondary if you have a separate trial/signup step.
For SaaS with trial: sign_up is primary if the trial is the conversion. purchase is primary if paid conversion is what you optimize toward.
For content sites: a single high-intent event like newsletter_signup_qualified (where you tag the qualified-quality subset) is better than marking newsletter_signup itself.
What NOT to mark as a Key Event: page_view, scroll, click, session_start, first_visit, view_item, add_to_cart. These fire too often and dilute the signal.
Step 3
Admin → Events. Find the event in the list. Toggle Mark as Key Event ON. Repeat for each event you decided on in step 2.
GA4 → Admin → Events. You'll see a list of all events GA4 has recorded in the last 30 days.
Find the event you want to convert (e.g., purchase). On the right side of the row, you'll see a Mark as Key Event toggle. Click it to ON.
Repeat for each event. You should end up with 2-4 toggles ON, not 10+.
If the event you want isn't in the list, it hasn't fired yet. Trigger it once (real or test), wait 24 hours, then return to mark it.
In late 2024, GA4 renamed the "Conversions" tab to "Key Events." If you're following older tutorials referencing Conversions, it's the same thing — just renamed.
Step 4
Admin → Events → Create event. Use this to derive new events from existing ones (e.g., "purchase over $100").
Sometimes you want a Key Event that's a subset of an existing event. Example: purchase over $100, or page_view of a specific high-value page.
In GA4 → Admin → Events → Create event. Click Create.
Custom event name: high_value_purchase. Matching conditions: event_name equals purchase AND value greater than 100.
Optionally copy parameters from the source event so they appear on the new one.
Save. Wait 24 hours for the event to fire. Then mark it as a Key Event in the Events list.
This is also the right path for tagging quality leads. Original event = generate_lead. Create event = generate_lead_qualified, matching condition = generate_lead WHERE lead_score > 7 (if you push lead_score in your dataLayer).
Step 5
Fire each Key Event once via DebugView. Confirm the event appears in Reports → Key Events within 24 hours.
Open GA4 → Admin → DebugView.
In a separate incognito browser tab, complete each Key Event action: make a test purchase, submit a test form, complete a test signup.
In DebugView, confirm the event appears within 60 seconds. Click it to see all parameters. Confirm value, currency, and other expected fields are populated.
Wait 24 hours. Then go to Reports → Engagement → Key Events. Each event you marked should appear with the count of times it fired.
If an event isn't appearing in the Key Events report after 24 hours but is appearing in DebugView, double-check that the Mark as Key Event toggle is actually ON in Admin → Events.
Step 6
Once Key Events are validated, import them into Google Ads (as Conversion actions) and Meta (as Custom Conversions) for ad optimization.
Google Ads import: Google Ads → Goals → Conversions → New conversion action → Import → Google Analytics 4 properties. Pick the GA4 property, select Key Events, import. (See the dedicated Link GA4 with Google Ads tutorial.)
Meta import: Meta Events Manager → Data Sources → your pixel → Custom Conversions. Create custom conversions that map to your GA4 event names IF you also fire the same events via Meta Pixel. GA4 doesn't push to Meta directly — they each need their own pixel.
TikTok and LinkedIn work similarly: each platform needs its own pixel + event mapping. GA4 is the analytics layer; the ad platforms each have their own tracking.
Why this matters: marking events as Key Events in GA4 alone doesn't optimize ad campaigns. The ad platforms need to know about the conversion too — either via direct pixel firing or via GA4 import (Google Ads only).
Step 7
Business priorities shift. Quarterly review of which events are Key Events keeps Smart Bidding pointed at what matters now.
Set a calendar reminder for the start of each quarter.
Go to GA4 → Reports → Engagement → Key Events. Review each Key Event's count and conversion rate trend.
Ask: does each event still represent what we optimize for? If your business model shifted from one-time purchase to subscription, your Key Events should reflect that.
Ask: are any events generating noise? If a Key Event fires 10,000 times/month but only 50 of those represent real business value, you've polluted Smart Bidding.
Remove the toggle from events that no longer represent business value. Add the toggle to new events that now do.
Common mistakes
Marking too many events as Key Events
What goes wrong: You mark page_view, scroll, add_to_cart, view_item, purchase, signup, and 4 more as Key Events. Smart Bidding tries to optimize for all of them. None gets enough signal. CPA inflates 30-50% because the algorithm spreads optimization across noise.
How to avoid: Limit to 2-4 Key Events that represent real business value. Everything else is a regular event — still tracked, just not optimized against.
Marking page_view as a Key Event
What goes wrong: Every page load counts as a conversion. Conversion rate looks like 90%. Ad reports become noise. New analysts who join the team are confused for weeks.
How to avoid: Never mark page_view as a Key Event. If you want to track high-value page views, create a custom event ("view_pricing_page") and mark THAT as a Key Event.
Using custom event names instead of recommended names
What goes wrong: You fire "complete_order" instead of "purchase." GA4 logs it but doesn't recognize it as an ecommerce event. Revenue reports show $0. Google Ads Smart Bidding gets weaker signal than it would with the recommended name.
How to avoid: Use GA4 recommended event names: purchase, generate_lead, sign_up, view_item, add_to_cart, begin_checkout, add_payment_info. Lowercase, exact spelling.
Not validating events before relying on them
What goes wrong: You mark an event as a Key Event but the underlying tracking is broken — the event only fires on 60% of conversions. You make 30 days of ad-spend decisions based on missing 40% of your data.
How to avoid: For each Key Event, validate in DebugView with a real test action. Confirm count in Key Events report after 24 hours. Periodically spot-check against your CRM/Shopify/Stripe ground-truth.
Forgetting to sync Key Events to ad platforms
What goes wrong: You mark purchase as a Key Event in GA4. You think you're done. But Google Ads has no idea the event exists — you never imported it. Smart Bidding runs blind. CPA stays high because the algorithm has no conversion signal.
How to avoid: Always complete the loop: Mark as Key Event in GA4 → Import to Google Ads via Goals → Conversions → set up Meta Custom Conversion separately. Each platform needs its own connection.
Counting "Once per event" when you want "Once per session"
What goes wrong: Default counting method is "Once per event" — fires every time. If purchase fires 3 times because of a duplicate, you count 3. Wrong.
How to avoid: For Key Events that should count uniquely per session (e.g., signup, lead), change Counting Method in Events → click the event → Edit. Set to "Once per session." Purchases stay at "Once per event" since each transaction is unique.
Recap
Done — what's next
How to set up Google Analytics 4 from scratch
Read the next tutorial
Hand it off
Picking the right Key Events isn't a technical decision — it's a strategy one. A specialist who understands your funnel can lock in the right event taxonomy in a single session and make sure every ad platform is optimized against the right signal. Typically $80-200 for the initial setup, $50-100/mo for ongoing audits.
See specialist rates
They're the same thing — Google renamed Conversions to Key Events in late 2024 to reduce confusion with Google Ads conversions. Functionally identical. Older documentation and tutorials still say Conversions.
For most businesses, 2-4. Ecommerce: purchase (primary), begin_checkout (secondary). Lead-gen: generate_lead. SaaS: sign_up + (sometimes) purchase. Marking more than 4 dilutes Smart Bidding signal and creates noisy reports.
No — Key Events are property-level, not campaign-level. They apply to all data in the GA4 property. If you need campaign-specific optimization signals, use audience targeting in Google Ads or create custom segments in GA4.
Three usual reasons: (1) tracking loss from ad blockers and consent rejection (5-15% gap is normal); (2) the GA4 event fires on form submit but your CRM only counts qualified leads (filter mismatch); (3) attribution windows differ. Compare apples to apples and accept reasonable gaps.
No. All events are tracked regardless. Marking as Key Event only changes whether the event shows in the Key Events report, can be imported to Google Ads, and feeds Smart Bidding. Most events should stay as regular events.
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