If you've ever installed two different applications that essentially do the same thing (music players, web browsers), you'll likely be presented with a small pop-up menu when trying to play a song or open a web page, asking you which application you'd like to complete the action with. Allowing the user to choose different applications to open certain content shows Android's flexibility, but it also slows you down. Luckily, you can tap "always" and never be bothered when performing that action again.
But what if you change your mind? What if an app update makes you reconsider which Twitter client, for example, you want to use to open Twitter links?
While setting a default application is very simple, clearing default apps is not as straightforward.
Note: I'm going to use home launchers as an example, but the steps are the same for any type of application, from browsers to Twitter clients to image viewers.
Setting default applications
In this example, I'll show you how to set a default application with two different home screen apps, Google Now Launcher and Nova Launcher. Since Google Now Launcher was pre-installed on the phone, it will always default to it when I press home, but after installing Nova Launcher, pressing the home button will present this pop-up menu.
To set Nova Launcher as the default application, simply tap its name, and then tap on Always. You're done! Now, every time you press the home button on your phone or tablet, Nova Launcher will automatically open instead of the menu you see above.
Clearing default applications
So lets say you set Nova Launcher as your default home screen replacement, but want Google Launcher back. Or, you try out a new image gallery, and don't like it, and want to go back to using the stock Gallery app. Any time you want to clear your default choice for an application type, all you have to do is pop into Settings.
Go into Settings and tap on Apps. Swipe left and right to change the list filtering between Downloaded apps, Running apps, or All apps.
Scroll down until you see Nova Launcher and tap on it.
Scroll until you see Clear Defaults button, tap it, and you're done. Now you'll be given the Select a home app menu again when you press the home button on your phone or tablet.
The procedure is the same for any app that sets itself as the default for performing a particular action, like an app that makes phone calls (such as Skype) making itself the default instead of your regular phone dialer. Just find the app in question in Settings > Apps, select it, and choose Clear Defaults.