Summary
The event must be designated as a key event. Only GA4 key events appear in the Google Ads conversion import list, so form_submission has to be marked as a key event under Admin, Data display, Events before it can be imported and used for bidding optimization. Once imported, set it as a primary conversion action so Smart Bidding actually optimises towards it.
Nitin Batra is a Google Analytics 4 certified professional who configures key events and Google Ads conversion imports for client properties as part of his regular measurement work.
Last updated: August 16, 2026
Before form_submission can be used for Google Ads bidding optimization, the event must be designated as a key event in GA4, since only key events are eligible to import as conversions into a linked Ads account.
- The event property must be linked to Google Search Console.
- The event must be designated as a key event.
- The event’s parameters must be marked as custom dimensions
- The event data must be analyzed in a custom exploration.
The correct answer is: The event must be designated as a key event.
Key Takeaways
- – The required first step is designating the form_submission event as a key event in GA4 before it can be used as a conversion in the linked Google Ads account.
- – You mark it under Admin, Data display, Events, using the Mark as key event toggle, and it appears in the Ads conversion import list after that.
- – Key events replaced the older conversions terminology in GA4, and they are the only events that feed conversion reporting and Google Ads conversion import.
- – Marking an event as a key event is not retroactive, so historical form_submission data will not appear as key event conversions for dates before you turned it on.
How many key events can I mark in a single GA4 property?
GA4 allows up to 30 key events per property, and the count includes any events you mark manually plus certain automatically counted ones like purchase. That limit is enough for most sites, but it forces discipline. Mark only the actions that genuinely represent business value, not every micro interaction on the page.
Where do I import a GA4 key event into Google Ads as a conversion action?
In Google Ads, go to Goals, Conversions, Summary, then New conversion action and choose Import, followed by Google Analytics 4 properties. The list that appears contains only key events from properties linked to that Ads account. Import the one you need, then confirm whether it should be a primary or secondary action, because only primary actions are used for bidding.
Does marking an event as a key event change how the data is collected?
No. Collection stays exactly the same, and the event parameters are unaffected. Marking a key event only changes how GA4 reports the event and whether it becomes available for conversion import and Google Ads bidding. This is why people often assume tracking is broken when in fact the toggle was simply never switched on.
Why does my key event show different counts in GA4 and Google Ads?
The two platforms count and attribute differently. Google Ads credits the conversion to the click date and uses its own attribution and conversion window, while GA4 reports the key event on the date it happened using the property’s attribution settings. Small gaps are normal. Large gaps usually point to a link configuration issue, consent differences or a mismatch in the date ranges being compared.