The feature is currently available on iOS
Apple users can now lock their WhatsApp chat using their phone’s biometric security.
The feature was first spotted by 9to5mach and is available with version 2.19.20 of WhatsApp.
Although you can’t secure your messages on a per-chat basis, the new layer of biometric security should give the contents of your messages more protection even if your phone itself is already unlocked.
To access the feature go to “Settings” –> “Account” –> “Privacy” before switching “Screen Lock” on.
Though users will still be able to view WhatsApp notifications (should they choose to display message previews) and quick reply within iOS, the full app won’t be able to be accessed unless the standard iOS authentication process is successful.
The feature may be released on Android too.