Safari is timing out or freezing after I go to one or two websites. Why?
Deleting all Cookies
Clearing my History
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Make sure you are on the latest software. Go to Apple menu > App Store > Updates and install any version of MacOS X and/or Safari that are available.
You can clear Safari caches manually:
Start or restart your Mac, then immediately press and hold the Shift key. The Apple logo appears on your display.
Release the Shift key when you see the login window. If your startup disk is encrypted with FileVault, you might be asked to log in twice: once to unlock the startup disk, and again to log in to the Finder.
From Finder press Command + Shift + G and enter the following path:
Remove Safari caches by placing them in the trash
Restart the Mac normally
Content re-worded from http://osxdaily.com/2015/01/18/troubleshoot-safari-freezes-crashes-mac-os-x/