Google's Pixel 4 face unlock feature works for Google Pay biometric authentication. Though using biometrics to authenticate payments in the app was already available, this was initially just for fingerprints.
On the Pixel 4 and Pixel 4 XL, the device obviously lacks this biometric sensor. As Google instead decided to go with face unlock as the only biometric option.
Face unlock support seems to have been added very recently to Google Pay through an update. This is rather quick timing, considering the Pixel 4 just officially hit retail stores this week.
Face unlock in Google Pay is for sending money
Before you go trying to use face unlock for authentication when making a payment at stores, know that it isn't required.
This is because Google Pay's face unlock support is for when you send payments to another person. It's also an alternative method for authenticating those payments, and not the only option.
There's already an option to type your PIN in directly after opting to send money. Google does this so that it can confirm you want to send off the currency.
Face unlock will basically replace this if you enable it. That being said, if you prefer using the PIN instead, keep the biometric toggle disabled.
You can find the biometric toggle in the app settings
If you want to enable the biometric authentication option but can't find it, it's located in the settings menu.
Tap the three lines button in the top left corner, and it'll open a side menu with a few options. The settings is one of those. Tap that, and you'll find an option for "sending money."
Here there are two toggles. One for requiring a PIN, and one for using biometrics instead. You can toggle both options, but there's no need if you have the face unlock enabled, as this will supersede the other.
Google Pay may be the latest app to support this new unlock method, but it's not the first. Last Pass beta has support for face unlock and added it earlier this week. It's also only available in the beta, though it will probably make the jump to the non-beta app in due time.
Once you toggle the biometric option on the Pixel 4 or Pixel 4 XL, you should see a confirmation request pop up. Along with that you will see a little picture of the face icon Google uses for face unlock. Tap the confirm button, and you're finished.
Now when you send money in the future, you can just look at your phone and the payment will be finalized.