If you're worried about the security of private files on your Android device, Google has your back: Google is adding PIN protection to its Files by Google app.

Google is introducing a new "Safe Folder" feature to its file storage app. To access that folder, users will need to enter a four-digit PIN. In addition, the contents of the safe folder will be locked as soon as you switch from the Files app to another app.

Files by Google is a non-native Android app that serves as a place to store files on your phone, manage storage, and transfer files between devices via Bluetooth.

Like other Android file managers, including those that may be installed on your phone, Files by Google also makes an attractive app for prying eyes to potentially sift through it, private or confidential files can be used as a place to hold files.

Some other file managers allow you to set a PIN to protect a given file, so Google is kind of playing catch-up.

But with various biometric and password protections already present on Android phones, one might wonder why the Files by Google app needs an additional level of security.

Well, it is designed for people who share their phones relatively frequently. For example, a child gives a smartphone to a friend to play a game or send a text message to a friend.

Google notes that in some cultures it is common for spouses, siblings, and children to share cell phones. This means that a device that passes through the hands of several pairs of people in a day is likely to appreciate having a secure place to keep private files.

"As part of Google's research, we're hearing from people like Shaina, a woman in Bangladesh, who says that she's not sure she'd be able to find a place for her children to go to school if she had to. Shaina's children use her phone for both learning and play after school," Google said in a blog post.

"Shaina worries about important files being accidentally shared or deleted. For Rashid, an Indian father, the lack of privacy means he cannot keep his identification on his phone, even if he needs it to apply for a job.

Even for those who do not share their smartphones, an extra layer of security can be useful if, for example, they want to ensure that sensitive work documents or risqué photos are stored securely.

Files by Google's Safe Folders feature is currently in beta, but according to Google, will be rolled out to more users "over the next few weeks."