Prevent or create duplicate tabs in Safari on Mac
When you’re surfing the web or researching a subject, avoid cluttering your window with multiple tabs for the same website. You can also purposely duplicate a tab to have another view into the same website.
Limit a website to one tab
In the Safari app on your Mac, begin typing a website address in the Smart Search field.
If you already have that address open in an existing tab, it appears below Switch to Tab.
Choose the website to use the existing tab.
Duplicate a tab
In the Safari app on your Mac, Control-click a tab or pin, then choose Duplicate Tab.