A default application is the program that Windows uses automatically when you open a particular type of file, such as a song, film, photo or web page.
For example, you might have more than one photo-editing application installed on your PC. You can choose one of them to be the default application that starts whenever you open a photo.
Swipe in from the right edge of the screen, tap Settings, then tap Change PC settings.(If you're using a mouse, point to the top-right corner of the screen, move the mouse pointer down, click Settings, then click Change PC settings.)
Tap or click Search and applications, then tap or click Defaults.
The default you choose will only apply to your account and won't affect other accounts on this PC.
On the defaults page, tap or click a current default application. If there is no default, tap or click Choose a default.
Tap or click a new default application.
The default email application must be one installed on your PC. You can't use a web-based email service, such as Outlook.com, Gmail or Yahoo! mail as the default email program.
You can fine-tune default applications based on the file type or protocol. For example, you can make all .jpg image files open using one application, and .bmp image files open using a different application.
On the defaults page, tap or click Choose default applications by file type or Choose default applications by protocol.
Tap or click a current default app, – Or – If there is no default, tap or click Choose a default.
When you change a default application for a file type or protocol, you can't leave it blank. You must select a new application.
You can make a program inaccessible without uninstalling it. For more information, see Setting program access and computer defaults.