There are two ways to change the default Web browser on a Mac computer running OS X Yosemite: from System Preferences or from the browser itself. Each browser gives you an option to move over your bookmarks and browsing history, so you can continue surfing the Web without missing a beat.
Using System Preferences
Click the Apple menu and open System Preferences. Click the General icon.
Click the Default Web Browser menu and select the browser you want to use. Some of the apps listed here may surprise you. If you have RealPlayer installed, for example, you can use its built-in browser as your Mac's default.
Click the red Close button. Your selection is saved automatically.
Remove your old default browser from the Dock if you don't want to see it anymore. Right-click its dock icon, or Ctrl-click it, select Options and then click Remove From Dock.
Moving to Chrome
Launch Chrome. To make Chrome your default browser, click the Menu icon in the upper-right corner and select Settings. Scroll to the bottom of the page and click the button that reads "Make Google Chrome the Default Browser."
Select Bookmarks from the Menu icon and select Import Bookmarks and Settings.
Click the From menu and select the browser you used to use. Specify the items you want to import -- Browsing History and Favorites/Bookmarks -- and then click the Import button.
Changing to Firefox
Launch Firefox and select Preferences from the Firefox menu. Click Make Firefox My Default Browser.
If you find another Web browser keeps making itself the new default, click the check box above this button. Firefox will then prompt you to make it the default browser again if it's ever dethroned.
Select Show All Bookmarks from the Bookmarks menu and then click the star-shaped Bookmarks icon at the top of the Library window. Select Import Data From Another Browser.
Select the browser you used to use. Click Continue.
Select the data that you want to import from Preferences, Browsing History, Bookmarks and Other Data. Click the Continue button to import that data to Firefox.
Changing Back to Safari
Launch Safari and select Preferences from the Safari menu. Click the Set Default button. When the confirmation window opens, click Use Safari.
Click the File menu, select Import From and then choose the browser containing your history and bookmarks.
Select Bookmarks and History or both. Click the Import button to copy the selected data to Safari.