Extensions are third-party developers add-on code that uses Safari's web features for specific tasks, such as making it easier to search Amazon, allowing an app, such as 1Password, to integrate with the browser and create an easy-to-use password management system, or adding an effective way to block pop-up ads.
You'll also find that most social media sites have Safari extensions that make posting to your favorite social site as simple as clicking a button in the Safari toolbar.
Instructions in this article apply to Safari 9 and later.
How to Download and Install Safari Extensions
Installing Safari extensions is an easy process. You can find a selection within Safari itself.
Open Safari and select Safari Extensions from the Safari menu.
The App Store opens to the Safari Extensions section. Scroll to find an extension you want to add. Downloading extensions is like buying anything else in the Mac App Store.
Click Get on a free extension or the price on a paid extension.
The Get button or price button becomes a green Install button. Click it to download the extension.
Your Mac may ask you to authorize the purchase even if the extension is free. Do so to continue the download.
To activate the new extension, return to Safari and select Preferences under the Safari menu.
The keyboard shortcut is Command+, (comma).
Select the Extensions tab in the Safari General preferences screen.
Click the check box next to the extension you downloaded.
Confirm the activation by selecting Turn on in the pop-up window.
To browse for additional add-ons, click the More Extensions button to return to the Mac App Store. Repeat these steps for all the extensions you download.
How to Use a Safari Extension
How you use a Safari extension depends on its functionality, but some elements are common to all of them. Generally speaking, you access and use an extension by clicking its icon on your Safari Toolbar. Once you do that, it runs an automated process or opens a menu to let you set preferences or select actions.
For example, the Grammarly extension runs automatically while you write, but you can open the menu to turn it off or on for a website.
How to Manage or Delete Safari Extensions
Once you start loading extensions for your Safari browser, you're probably going to want to manage their use or uninstall the extensions you don't like or just never use.
Return to the Extensions pane of Safari's Preferences pane.
Click the name of the extension you want to remove in the left pane.
To temporarily disable the extension, remove the check mark from the box next to it.
To remove an extension completely, click Uninstall in the right pane.
You can redownload extensions you've uninstalled as long as they're still available in the App Store.
Where to Find More Safari Extensions
The App Store isn't the only place to download Safari extensions; it's just the easiest. You can also find them on other sites with a quick internet search.
Safari extensions are generally safe to install. Apple requires all extensions to run within the basic tools it provides in the Safari extension environment. You don't necessarily have to worry that one you download outside of the App Store will wreck your computer but make sure you trust the developer before you install anything they made.