Use the Google Ads tag for the conversions you bid on and GA4 key events for cross-channel reporting. Google lets you use both, but only the Google Ads tag records view-through conversions and supports the multi-source conversions beta. If you track the same action both ways, make only one version primary so bidding doesn't count it twice.
You don't have to choose only one. Google's help center says you can use any combination of Google Ads conversion tracking and imported Google Analytics conversions at the same time. The real question is which one Smart Bidding should optimize for, because the two measure differently.
How are they different?
| Google Ads tag | GA4 key event imported into Google Ads | |
|---|---|---|
| View-through conversions | Yes | No, Google says these need native Google Ads measurement |
| Multi-source conversions (beta) | Yes, for website actions set up with code | No, deduplication has to happen inside GA4 first |
| Other channels | Measures Google Ads interactions only | In GA4, the same event also shows organic channels such as search, email and social |
A GA4 import is not a worse conversion, it is a different one. GA4 is built to show the whole journey across channels, while the Google Ads tag only cares about the ad interactions that led to the conversion.
Which one should Smart Bidding use?
I use both: the Google Ads tag version of a conversion as primary, and the GA4 import of the same action as secondary. The tag gives bidding the most complete picture of what your ads did, including view-through conversions, and it works with the multi-source conversions beta. GA4 stays useful as a cross-check and for seeing how paid traffic fits next to your other channels.
A GA4 import as the primary action can still make sense when your tracking lives entirely in GA4 and you don't want to maintain a second setup. If you go that way, two things to know: Google sets actions created in the GA4 interface to secondary, so you have to switch them to primary before bidding uses them, and historical data from before the import isn't included.
How do you avoid counting the same conversion twice?
- Make only one version primary. If a purchase is tracked by the tag and by a GA4 import, and both are primary, bidding sees two conversions for one sale.
- Don't double-tag. Google warns that double-tagging your site can cause duplicate conversion reporting.
- Expect the numbers to differ. Google Ads reports a conversion on the date of the click, while Google Analytics reports it on the date it happened. Attribution and counting settings add more gaps. I explain these in why Google Ads and Google Analytics show different numbers.
Before you trust either source, test that your conversion tracking fires correctly. If you use the tag, adding enhanced conversions is the next step.
Sources
- Google Ads Help: Create conversions from Google Analytics events in Google Ads - https://support.google.com/google-ads/answer/2375435?hl=en
- Google Analytics Help: Create Google Ads conversions based on Google Analytics key events - https://support.google.com/analytics/answer/10632359?hl=en
- Google Ads Help: FAQs about Google Ads multi-source conversions (beta) - https://support.google.com/google-ads/answer/17111689?hl=en
- Google Analytics Help: Creating and managing conversions - https://support.google.com/analytics/answer/14710559
- Google Ads Help: Set up your web conversions - https://support.google.com/google-ads/answer/16560108?hl=en