WhatsApp has been working on Fingerprint support on Android for a long time now and the latest update has finally enabled it for the Beta users. The latest beta has also bumped the app to v2.19.221.
The fingerprint unlock feature has been available on iOS for while now but Android users will need to wait as the feature is currently available just for the beta users. If you’re using beta then you can head to Settings > Account > Privacy to enable Fingerprint Unlock. The feature will work on Android Marshmallow and above. WhatsApp has also added an option to hide message content in notifications preview if the fingerprint unlock is enabled. The message content will also be hidden if you’re using WhatsApp widget on the home screen.
As mentioned above, the feature is currently available for beta users. WhatsApp is expected to roll the feature out to the public once the beta testing is complete.