It’s not hard to do this using tools baked into current versions of Android or a third-party app. Here are a few strategies that you can try. (Note: these directions are for a Pixel XL running Android 9. The interface of your phone many vary somewhat, depending on the manufacturer, model, and OS version.)

Set a data limit

You can have your phone issue a warning if you’re nearing your data limit before the end of your monthly billing cycle. You can even set a limit beyond which your phone won’t use any data.

• Go to Settings
• Go to “Network & internet” > “Data usage” > “Data warning & limit”
• Tap on “App data usage cycle.” This will let you set the day that your account starts its monthly cycle.
• Back up and toggle “Set data warning” on. You can then enter the data limit — say, 4GB — that you want for your phone.

On the same page, you can toggle “Set data limit” on. This will turn off your mobile data completely when it hits whatever limit you set.

Use Data Saver mode

If you have Android 8.0 or later, your phone should come equipped with Data Saver mode, which kicks in when you’re not on Wi-Fi and ensures that apps and services that are not being actively used won’t be able to stream data in the background.

It’s very easy to turn Data Saver mode on and off.

• Go to Settings
• Go to “Network & internet” > “Data usage”
• Select “Data Saver.” Toggle “Use Data Saver” on.

There may be specific apps that you want to allow to use background data, even when Data Saver mode is on. For example, you may want to get Twitter notifications no matter where you are.

• Go to the “Data Saver” page (see above)
• Tap on “Unrestricted data”
• Scroll down to any apps that you want to enable for background data use even when Data Saver mode is on. Toggle them on.

Use a data management app

While Data Saver can help you manage which apps are allowed to work in the background, you may want more detailed control of your data. In that case, an app such as Google’s Datally, My Data Manager, or one of several available data management apps can help.

Datally, for example, will not only automatically prevent apps from working in the background, but it will also allow you to set a daily data limit and a bedtime mode, create an emergency bank of data (in case you run low toward the end of the month), and monitor hot spot usage (which, as I know to my regret, can destroy a month’s data allowance in short order).

Another popular app, My Data Manager, tracks data usage across single and multiple devices, arranges for alerts, checks data usage across a family plan (so that you’ll know who used 75 percent of that month’s data allowance), and tracks consumption so you can figure out whether you should switch to a different plan.

The advantage of all these apps is that you can treat them as set-and-forget tools, allowing them to do their thing in the background, or you can continually tweak them to fit your needs as you go. Either way, you — and your data plan — are the winners.