Conversion tracking in GA4 answers the question that traffic data alone cannot: is your website actually producing business results? Without it, you know how many people visited but not how many did something valuable. Every channel attribution decision, every budget allocation and every performance report depends on conversion data being accurate. A significant proportion of GA4 properties have event configuration errors causing incomplete data, and many businesses are optimising based on data that captures only a fraction of actual conversions.
At Gorilla Marketing, conversion tracking configuration is the first thing we set up for analytics and tracking clients. Before any SEO or PPC reporting can be meaningful, the platform needs to know what counts as a win. This guide walks through the full setup process, from identifying what to track through to verifying the data is flowing correctly.
Key Events vs Conversions: The Terminology Shift
Google renamed conversions to “key events” in GA4 in March 2024. The functionality is identical. A key event is any event you’ve marked as important to your business. All metric names changed too: “session conversion rate” became “session key event rate”, “user conversion rate” became “user key event rate”.
The exception is Google Ads. Within the Ads interface, the term “conversions” still applies. When a GA4 key event is linked to Google Ads, it becomes a conversion for bidding purposes. This matters if you run paid campaigns, because what GA4 calls a key event is what Google Ads uses to optimise bids.
GA4 also pre-marks certain events as key events by default: purchase, first_open, app_store_subscription_convert and app_store_subscription_renew. For most websites, purchase is the only relevant default.
This guide uses both terms interchangeably. The setup process is the same regardless of which label the interface shows.
Deciding What to Track
Not every user action deserves to be a key event. GA4 enforces a limit of 30 key events per property, and marking too many dilutes the data and clutters reporting. The principle: a key event should represent a completed action with direct or strong indirect business value.
Primary conversions are actions that directly generate revenue or leads. Purchase completions, form submissions, phone calls, quote requests and booking confirmations. Every business should have at least one primary conversion configured.
Secondary conversions indicate strong intent but aren’t the final step. Adding to basket, starting a form without completing it, downloading a resource or visiting a pricing page. These are useful for funnel analysis but should stay as regular events, not key events, unless you specifically need them for Google Ads bidding.
A common mistake is marking page views, scroll events or video plays as key events. These are engagement signals, not business outcomes. Track them as events for analysis, but keep key events focused on actions that matter commercially. The 30-event limit means every slot should count.
Three Ways to Set Up Key Events
GA4 offers three routes to conversion tracking, each suited to different situations.
Method 1: Mark an existing event as a key event
GA4 automatically collects certain events, and Enhanced Measurement tracks others like scroll depth, outbound clicks, file downloads and video engagement. If the action you want to track is already appearing as an event, simply mark it.
Navigate to Admin > Events. Find the event in the list and click the star icon to mark it as a key event. Alternatively, go to Admin > Data Display > Key Events > New key event and enter the exact event name. The event immediately begins counting as a conversion. No code changes required.
This works well for events Enhanced Measurement already captures, like file_download or form submissions if your platform fires a built-in event. One important detail: the event must have already been logged at least once before it can be marked as a key event. Marking an event name that hasn’t been logged yet can produce “(not set)” values in reports.
Method 2: Create a new event in the GA4 interface
If the action isn’t already appearing as an event, create a custom event within GA4 based on conditions applied to existing events.
Navigate to Admin > Events > Create Event. Name it descriptively following GA4 naming conventions: lowercase, underscores instead of spaces, no special characters, maximum 40 characters. Examples: contact_form_submission, quote_request_complete.
Set the matching conditions. The most common pattern for form tracking: match the page_view event where page_location contains a thank-you page URL. If submissions redirect to /thank-you/, create an event that fires when page_location contains that path.
Wait up to 24 hours for the event to appear in the Events list, then mark it as a key event. Note that this method doesn’t backfill historical data. Conversions only count from the moment the key event is active.
This works for straightforward scenarios. For anything more complex, Google Tag Manager provides significantly more flexibility.
Method 3: Google Tag Manager
For most professional setups, GTM is the preferred route. It provides granular control over when events fire, what parameters they carry and how they interact with other tracking.
Step 1: Identify the trigger. What user action should fire the event? Common triggers: form submission, click on a specific button, loading a confirmation page, custom data layer events pushed by the website.
Step 2: Create the trigger in GTM. Open Tag Manager > Triggers > New. For form submission, select Form Submission trigger type. For a button click, use Click with filters for the CSS selector, ID or text. For data layer events, use Custom Event and specify the event name your site pushes.
Step 3: Create the GA4 event tag. Tags > New > Google Analytics: GA4 Event. Enter your Measurement ID (found in GA4 under Admin > Data Streams). Name the event following naming conventions.
Step 4: Add event parameters. Parameters provide context. For a form submission: form_name (which form was submitted), form_destination (the email it sends to), form_value (if monetary). Register important parameters as custom dimensions in GA4 under Admin > Custom Definitions so they appear in reports.
Step 5: Attach the trigger and test. Connect the trigger from Step 2 to the tag. Save and move to testing before publishing.
Testing with DebugView
Never publish conversion tracking without testing. DebugView shows events firing in real time so you can verify triggers and parameters.
Enable debug mode. Install the Google Analytics Debugger Chrome extension, or add the debug_mode parameter to your GA4 configuration tag in GTM.
Open DebugView. GA4 Admin > DebugView. Visit the page where the conversion should fire and complete the action.
Verify the event. It should appear in the timeline within seconds. Click it to inspect parameters. Confirm the event name matches your configuration and parameters contain expected values.
Check for duplicates. If the same event fires twice for one action, you have a duplication issue. This most commonly happens when Enhanced Measurement and a GTM tag both track the same interaction. Disable one.
Use GTM Preview mode alongside DebugView. Preview mode shows which tags fired, which triggers activated and what data was sent. Together with DebugView, this gives you a complete picture of the tracking chain from trigger to GA4.
A Practical Debugging Workflow
When conversions aren’t appearing or numbers look wrong:
Check DebugView first. Is the event firing at all? If not, the trigger isn’t working. Check GTM Preview mode for trigger conditions that aren’t being met.
Event fires but isn’t in reports? Verify it’s marked as a key event. Check that 24 to 48 hours have passed since marking.
Numbers too high? Look for duplicate events. Check event count per user in reports. Values consistently above 1 for a form submission event suggest duplication.
Numbers too low? Check consent mode configuration. Check whether ad blockers or privacy tools are suppressing the tag.
“(not set)” appearing? The event may have been marked as a key event before it was ever logged. Log it first, then mark.
Counting Methods
GA4 offers two counting methods for key events. Choosing the wrong one skews data significantly.
Once per event counts every instance. Two form submissions in one session equals two conversions. Appropriate for e-commerce purchases or any action where each instance has independent value.
Once per session counts a maximum of one per session. Appropriate for lead generation where one form submission is the meaningful action and subsequent submissions are duplicates.
Change this in Admin > Key Events. Click the event and select the counting option. The default is “once per event”, which is correct for e-commerce but overstates conversions for lead generation. This is one of the most common configuration mistakes we see in client audits.
Event Naming Conventions
Consistent naming prevents confusion as tracked events multiply. GA4 enforces a 500 distinct event limit per property (separate from the 30 key event limit), and poorly named events waste that allowance.
Use action_object format: form_submit_contact, purchase_complete, download_brochure, click_phone_number. Lowercase with underscores. No spaces, capitals, forward slashes or hyphens in event names.
Document every event in a tracking plan. A spreadsheet listing each event name, trigger, parameters and key event status prevents the setup from getting disorganised. This becomes essential when multiple people manage the GTM container or when troubleshooting months after initial setup.
Enhanced Conversions
Enhanced conversions improve conversion measurement by sending hashed first-party customer data (email address, phone number, name, address) alongside standard conversion tracking. Google matches this data against signed-in user accounts to attribute conversions that would otherwise be lost to cookie restrictions and cross-device journeys.
The impact is measurable: businesses typically see a 5 to 15% increase in reported conversions after enabling enhanced conversions, with match rates improving by 10 to 40%.
Setting up enhanced conversions:
For GA4, navigate to Admin > Data Streams > select your stream > Enhanced measurement > turn on user-provided data collection. GA4 can automatically detect form fields containing email and phone data, or you can configure specific fields through GTM using data layer variables.
For Google Ads, enable enhanced conversions in the Google Ads interface under Goals > Conversions > Settings. Three collection methods are available: automatic (form field scanning), code-based (JavaScript snippets) and GTM (data layer variables). All data is hashed with SHA-256 before transmission.
A healthy benchmark: 50% or more of conversions showing as “enhanced” in the Google Ads diagnostics report indicates proper setup. Below that, check that forms are correctly identified and that hashing is working.
Connecting Key Events to Google Ads
If you run Google Ads, linking GA4 key events enables conversion-based bidding. Without this connection, Smart Bidding has no data to optimise against.
Link accounts in GA4 under Admin > Product Links > Google Ads Links. Ensure auto-tagging is enabled in the Google Ads account settings. Once linked, key events appear in Google Ads under Goals > Conversions. Select which are primary (used for bidding) and which are secondary (observed only).
One critical warning: never have both a GA4-imported conversion and a separate Google Ads tracking tag active for the same action. This double-counts conversions and corrupts Smart Bidding optimisation.
For businesses running both SEO and PPC, using the same key events for both channels ensures consistent measurement. GA4 provides unified conversion data across organic and paid traffic, which matters when comparing channel performance and building attribution models.
Understanding Conversion Metrics in GA4
GA4 provides two conversion rate metrics that are frequently confused:
Session key event rate = sessions with at least one key event divided by total sessions. This is the metric most people mean when they say “conversion rate.”
User key event rate = users with at least one key event divided by total users. Higher than session rate because a returning user who converts on their second visit counts as a converting user.
A common reporting error: mismatching scopes. Using a session-scoped metric with a user-scoped dimension (or vice versa) produces misleading results, sometimes showing 100% conversion rates. Make sure dimensions and metrics use the same scope.
Common Mistakes and How to Avoid Them
Tracking thank-you pages without filtering. If a conversion fires on /thank-you/ loading, anyone who bookmarks or refreshes that page generates a false conversion. Add conditions: require arrival from the form page or a preceding form event.
Not accounting for consent. Users declining analytics cookies aren’t tracked. Actual conversions are higher than reported. Consent Mode v2 helps by modelling unconsented conversions, but a gap remains. Global cookie acceptance rates average around 31%.
Duplicate event firing. Enhanced Measurement and GTM both tracking the same action. Form submissions are the worst offenders. Audit Enhanced Measurement settings against your GTM container.
Missing cross-domain tracking. Conversion on a different domain (booking system, payment platform) breaks session continuity. The conversion gets attributed to the booking domain as a referral rather than the original traffic source.
Not testing after site changes. A redesign, CMS migration or form plugin update can silently break tracking. Build verification into every site change process.
Not excluding internal traffic. Employee and developer visits triggering conversions inflate numbers, particularly damaging for small businesses with low conversion volumes. Exclude internal IP addresses in GA4 under Admin > Data Streams > Configure tag settings.
Verifying Data Accuracy
After setup, verify conversion data against reality. Compare GA4 key event counts to actual business outcomes: form submissions to emails received, purchases to payment records, phone clicks to call logs.
A perfect match is unusual. Consent gaps, ad blockers, bot traffic and timing differences create discrepancies. GA4 typically captures 15% fewer conversions than Universal Analytics did in comparable setups. But the numbers should be in the same range. GA4 showing 50 form submissions when the inbox has 120 means something is broken. GA4 showing 50 when the inbox has 55 is normal.
Set up monthly reconciliation. Five minutes comparing GA4 counts to actual outcomes catches tracking failures before they corrupt months of data.
What Comes After Setup
Conversion tracking is infrastructure, not insight. The value comes from what you do with the data.
Use conversion data to evaluate which SEO efforts drive business results rather than just traffic. Connect conversions to landing pages to find which organic content produces leads or sales. Compare conversion rates across channels to allocate budget where it generates the best return. Build attribution models to understand how touchpoints contribute across the full journey.
GA4 conversion data also powers audience building and remarketing. Converters can be excluded from acquisition campaigns. Near-converters can be retargeted. Server-side tracking can recover additional conversion signals that client-side tracking misses, further improving the accuracy of the data powering these decisions.
Gorilla Marketing’s analytics and tracking service includes full conversion tracking setup, GTM configuration, enhanced conversions, ongoing data verification and reporting that connects tracking data to business outcomes. Get in touch if your current setup isn’t giving you reliable conversion data.
