Go to the website.
Choose Safari > Settings, then click Websites.
Click Pop-up Windows on the left.
If you don’t see Pop-up Windows, make sure you scroll to the bottom of the list.
In the pop-up menu for the website, choose one of the following:
Block and Notify: Pop-ups for the website don’t appear, but when you visit the website, you can choose to show them by clicking Hide distractions when reading articles in Safari on Mac