Lockdown Mode is an optional, extreme protection that’s designed for the very few individuals who, because of who they are or what they do, might be personally targeted by some of the most sophisticated digital threats. Most people are never targeted by attacks of this nature.
Turn on Lockdown Mode
To exclude a website while browsing: Choose the Safari menu > Settings for [website]. Then deselect the Enable Lockdown Mode checkbox. To include the website again, reselect the checkbox.
From the menu bar in Safari, choose the Safari menu > Settings
In the sidebar, scroll down and click Lockdown Mode
From the menu next to a configured website, turn Lockdown Mode on or off.