In some cases, apps won't stay in the background ("alive" or in a sleep mode) due to Android OS optimization function, or so called "battery save mode" — this function can kill background applications. It may be inconvenient to relaunch them each time they are getting closed. To avoid the background app termination you need to follow these steps which we described separately for each manufacturer (version) of Android OS. Note that instructions for different manufacturers are mostly very similar.
List of manufacturers with different versions of Android OS:
To set up AdGuard's background work for Xiaomi devices you should pay attention to Battery and Permissions.
Go to "Battery"
Select "battery saver" app
Find and select AdGuard
Go to "Permissions"
For Samsung devices, there is no huge need for setting up the background work, but if in your case the application is getting closed or disappears from the recent tasks after a while, do the following:
Tap on the "recent tasks" button, tap on the "additional settings" icon. It should look like this:
Tap on "Lock Apps":
Huawei devices are the easiest to set up, it is enough to perform two simple steps to lock the application in the background so it won't be terminated by battery saving or background killer process.
Devices with OxygenOS on board are the most problematic, with its OS-sepcific cache cleaning and free RAM, including OS optimization. In addition, OxygenOS can interrupt the application's work if you do not use it for a while. To avoid these unwanted consequences, follow these steps:
Go to Settings
Battery > Battery optimisation
Find the app you want to keep awake all the time
Tap on it and select "Don't optimize" option
Tap "Done" to save
Android stock OS normally does not conflict with applications working in the background, but if you are facing any issues you will need to switch on the "Always on VPN" mode.
Go to Settings - Network and Internet
Tap on "VPN" and choose AdGuard
Set up "Always on VPN" mode