Extra security feature slows things down but could stop prying eyes
The company recently unveiled biometric tools in the iPhone version of the app which mean that the phone will check you're the right person before allowing you in. The setting means that you can only open WhatsApp if you have the right fingerprint or face, just like when you unlock your phone.
It means that anyone who shares their phone around or is likely to have it unlocked can keep messages secret, even if other apps aren't locked up.
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The feature involves a slight trade-off: it's much harder for anyone to get into your chats, but it's also a little harder for you to do so, too. You'll be forced to show your face or your fingerprint every time you try and message someone.
The feature is very easy to turn on: open WhatsApp's settings, head to the Privacy option, and click it to on. WhatsApp will ask you whether you want the phone to lock straight away, if it has not been used for an hour, or for time limits in between.
While you're in those settings, there might be other privacy options that you'd like to turn on. It is worth having a full look through all of those pages.
There's one thing to beware of: even though the feature locks access to the app, it doesn't lock the notifications. That means if someone has your phone then they'll still be able to see messages when they come in, and will even be able to reply to them if they pull down and use the quick reply feature.
That can be turned off easily, though it once again means sacrificing ease for security. To do so, head into the notifications option in the Settings app, click on WhatsApp and turn off "show previews".
The same can be done with other apps, though many have not yet integrated the biometric settings and so anyone with your phone is likely to be able to get into your messages. Apple does not offer a way to lock specific apps, meaning that developers have to introduce the features if they are to be included.