Mobile internet data can be expensive, especially if you spend a lot of time out of range of Wi-Fi signals. Things get worse when you realize how many apps use internet data in the background even when they're closed.

Fortunately, Android phones have a way to reduce how much internet these background apps hog up: Data Saver mode.

Data Saver is a feature built into Android phones that limits how much data your apps can use in the background when you're not connected to Wi-Fi.

While Data Saver is on, if an app is running in the background, it won't be able to connect to the internet. This means that it won't receive updates, won't send you push alerts, and won't take any of your data. This mode is great if you've used up a lot of your monthly data.

It's also useful if you're low on battery. Less apps updating in the background means less power usage, which lets your phone battery last longer.

Some apps that you're actively using might connect to the internet less, too. For example, some apps might not load images until you tap on them.

Here's how to turn it on or off.

You'll find Data Saver grouped together with the rest of your Android's networking settings.

1. Open your Android's Settings app and tap Network & internet, then Data Saver.

2. Tap the Use Data Saver option at the top of the page to flip the switch to the right and turn it on.

When you want to turn it off, come back to this page and flip the Use Data Saver switch to the left.

Some apps need constant internet access to work properly. That's why Data Saver lets you exclude certain apps from the restrictions.

To let apps use data even while you have Data Saver on, head back to the Data Saver menu and tap Unrestricted data. You'll see a list of every app on your device — find the app you want and flip the switch next to it.