Hey Bryan, the easiest way is to use WhatsApp’s built-in lock feature—no extra apps needed.
- On Android: open WhatsApp, tap the three dots (⋮) > Settings > Account > Privacy > Fingerprint lock. Toggle it on and set “Require fingerprint” to immediately or after a delay.
- On iPhone: go to WhatsApp > Settings (bottom right) > Account > Privacy > Screen Lock. Enable “Require Face ID/Touch ID” and choose “Immediately” for maximum security.
If you’re on an older OS that doesn’t support these options, you can try a reputable third-party app locker (like AppLock for Android) but built-ins are more reliable.
Make sure you also secure your phone’s lock screen with a PIN or biometric lock so no one can bypass WhatsApp’s gate.
Let me know if you hit any snags!