As stated, the Firestick Fast Task Killer works on all Firestick and Fire TV devices. You can always test to see how the application works by opening one of the apps you have installed on your device, for example, Netflix.
When any application starts from fresh, it usually prompts you by asking which profile you want to use. You can choose your profile and the app will open up.
When you press the home key and go back to the home screen then try to open the app again, you’ll notice that it doesn’t ask you which profile to use like it did the first time you opened it. This is because the application is still running in the background. That’s basically how you can test to see if an application is running in the background.
Most of the apps installed on your Firestick will normally give you a similar prompt when you open them for the first time. But once they start running in the background, they’ll open automatically without asking you which profile to use.
You can choose this hard way to check each app and see if it’s running in the background or simply use the Firestick Fast Task Killer to close all background apps in one click.