Safari extensions are software files that can modify Safari’s behavior and appearance. They can provide extra toolbars in the Safari window, add buttons to the Safari toolbar, add items to contextual menus, manage Safari’s windows and tabs, and modify the behavior and appearance of webpages.
Here are some examples of extensions:
A toolbar that provides access to Facebook, even when you’re viewing another webpage
An advertisement blocker
A graphical tab switcher
Because extensions can modify the behavior of Safari, you should download and install extensions only from trusted sources.
Safari extensions have the filename extension “.safariextz”.