Article: In Safari, add-ons are referred to as "plug-ins". Click Help → Installed Plug-ins. This will open a new page that lists all of your installed plug-ins. You will be shown the file name for the plug-in (for example the QuickTime file is called "QuickTime Plugin.plugin"). You won't be able to uninstall the plug-in from within Safari, so make note of the file name. OS X has hidden the Library folder, which is where the add-on files are stored. You will need to unhide the Library folder to find the plug-in file.  Open your Home folder in Finder. Click View → Show View Options. Check the "Show Library Folder" box. Refer to the file that you noted in Step 2. Navigate to the folders that contain the plug-in files. The plug-in files may be located at Library/Internet Plug-Ins/ or ~/Library/Internet Plug-ins/. Click and drag the plug-in file to the Trash. Restart Safari for your changes to take effect.

What is a summary?
Open your list of installed plug-ins. Find the plug-in you want to remove. Enable your Library folder. Find the plug-in file that you want to remove. Delete the file.