Standby Apps are placed in Standby Buckets that segregate apps into different categories, each of which defines limits on device resources (such as CPU and Battery). There are four categories in which a Standby App can be placed.
Active: The system does not place any restrictions on the app's ability to run jobs or trigger alarms.
Working_Set: The system imposes mild restrictions on its ability to run jobs or trigger alarms.
Frequent: The system imposes stronger restrictions on its ability to run jobs and trigger alarms, and also imposes a cap on high-priority Firebase Cloud Messaging (FCM) messages.
Rare: The system imposes strict restrictions on its ability to run jobs, trigger alarms, receive high-priority FCM messages, and limits its ability to connect to the internet.
For more information on power management restrictions, see this Android Developers page on the subject.
From top to bottom, the categories will place increasing restrictions on an app. That means if you have an app you want to limit, you can now do that manually. This is a handy way of limiting what an app can access. Say, for instance, you have an app that you use locally (for a specific purpose), but want the app to only have limited access to the internet. With Standby Apps, you can make that happen. But how? Let's find out.
What you'll need
There are two requirements for Standby Apps:
Android Pie
Developer Options enabled
If you have a device running Android Pie, you only need to enable the Developer options. How do you do that? Simple. Open the Settings app and go to System | About Phone and tap Build number five times. After the fifth tap, Developer Options will be enabled.
Changing an Apps Standby category
Go back to the Settings app and then navigate into System | Developer options | Standby apps (way down at the bottom of the Developer options window). Tap Standby apps, and you'll see a listing of all your installed apps (Figure A).
Figure A
Locate and tap the app you want to modify. A pop-up window will appear, listing the four Standby categories (Figure B).
Figure B
Figure B
The Standby categories.
Tap the category you want to add the app into, and the pop-up will be dismissed. You've effectively changed the system limits on that application.
Manually limit your apps
This hidden feature is a great way to manually limit your apps, especially if you have an app that could cause problems on your device. Give this feature a try and see if it doesn't give you more control over your Android devices and the apps installed. Remember, however, if you change the category for an app, and you find that the app isn't functioning properly, change the category back to its original, and it should behave as expected. Problems can arise because app developers will have set their own criteria for how non-active apps are assigned to buckets. So, again, if you find issues arise after making the switch, simply switch the category back.