You already know that it isn't a good idea to just hop on any public Wi-Fi network. You might be logging into the Wi-Fi of a hacker disguised as the Wi-Fi network of a restaurant.

But there's a little known feature in Facebook you've probably never noticed, that shows you who has free Wi-Fi and the name of the network and gives you directions to it.

You'll find it using the Facebook app on a mobile device. Tap the more icon, the three lines, at the bottom of the screen. There you'll see "find Wi-Fi".

To use it, you'll need to give the app permission to use your location. Not just when you're using the Facebook app, but always. That may run down your smartphone battery a little faster. You can always change the setting when you're not using it.

It'll open a map of your location and the nearest public Wi-Fi network to you. Other networks are marked. Tap one to get the name, address, directions and to visit the business' Facebook page.

You'll be able to see the name of their Wi-Fi network too. That's a cool safety measure to keep you from logging into a network that could steal your information.

Where does Facebook get all this? From the business's Facebook page, if they entered their Wi-Fi hotspot information.

You can also adjust the map to another area you're going to be visiting. Select the area and search.

This is a feature only available in the Facebook app, you won't be able to find Wi-Fi using the Facebook website.

It's a good idea when you visit one of those businesses to ask someone who works there for the name and password of the network, to make sure you're getting on the right one.