Changing the default application for most files is easy in OS X. OS X also allows you to choose your default web browser and email client, but these options are hidden in places you might not expect.
Some browsers and email clients may provide that automatically become the default when you start them for the first time, but if they don’t-or if you want to change it later you will have to find the OS X settings for these.
How to Change The Default Web Browser
To change the web browser, you need to use the system preferences window. To open it, click Apple menu> System Preferences.
Click the “General” icon in the upper left corner of the “System Preferences” window.
Click the “Default Web Browser” box here, and select an installed Web browser.
If you don’t see the “Default Web Browser” option here, you may be using an older version of Mac OS X. In OS X Mavericks and earlier, the option to change the default web browser is in the preferences of Safari. Launch the Safari browser and click Safari>Preferences. Click the “Default Web Browser” option under the General tab, and then select your preferred Web browser.
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Choose Your Default Email Client
To change the default email client, you need to open the mail application included in your Mac and change the default email client from there. Yes, it’s a bit weird-you need to use the default mail application to change your email client, even if you don’t want to use the mail application for anything else.
First, open the mail application. If there is no icon on your Dock, you can press Command + Space to open Spotlight search, type “Mail”, and press Enter. You can also open a Finder window and go to “Applications”> “Mail”.
Click Mail>Preferences to open the preferences window of the mail application.
Click the “Default Email Reader” option on the General tab and select your preferred email application.
Apps will only show up in these lists (if they are installed), so you must install a web browser or email client before they can show up here.