With Windows 10, you can quickly and easily change your default Web browser...as well as your default app for reading email, viewing photos, playing music, and more. Here's how to go about it.
Pop open the Start menu and go to Settings. Select System, then select Default apps. Here you can change your default calendar, email, mapping, music, photo, video, and Web browsing apps.
To set a default app for any of these, click the current default app's name. (If you don't have a default app set, "Choose a default" will appear in place of an app's name and icon.) A menu will pop up with whatever apps you have installed that can handle each task: pick the app you want to use for each task, and Windows will change your default apps accordingly.
You can also look for new apps to buy and download by selecting Look for an app in the Store from the menu.
If you ever decide to return to the default...erm...defaults, scroll down to "Reset to the Microsoft recommended defaults" then press the Reset button.
While Microsoft's basic Default Apps settings are pretty straightforward, you can get really granular if you want.
Do you want to set default apps by file type? Scroll down and select Choose default apps by file type. You'll get a massively long list of file types and the apps set to open them: Scroll down to the file type for which you want to change the default app, then select the default for that file type as you did before.
You can also decide which protocol is associated with which app—useful if you want to set your default FTP client, for example. To get to this screen, select Choose default apps by protocol. You may never have the need to mess with these settings, but they're there if you need them.
Finally, if you prefer the older, Windows 7-style default apps settings screen, select Set defaults by app.