about:blank macOS installation instruction

Activate the "Start at login" option to let about:blank synchronize the blocked URLs.

Open Safari.

Go to the top menu bar & click on Safari.

Select 'Preferences...' in the dropdown.

A new window should appear now. Click on 'Extensions' in the top bar of that window.

You should see about:blank on the left side of the window now. Check the checkbox to activate about:blank.