The feature lets you lock and move individual chats to a secure, password- or biometrics-protected folder. The contents of such chat will also be automatically hidden in notifications, so no one can see what you're talking about and with whom.
To lock a chat, tap the name of a one-to-one or group conversation and select the lock option. To display these hidden chats, simply pull down on your inbox and enter your phone password or complete a biometric scan.
“We think this feature will be great for people who have reason to share their phones from time to time with a family member or those moments where someone else is holding your phone at the exact moment an extra special chat arrives,” the company wrote in a blog post.
The Chat Lock is rolling out now, and it will get additional upgrades over the next few months, including locking for companion devices and creating a custom password for each chat so users can use a unique password different from their phone's.