Use tabs for web pages in Safari on Mac
When you’re surfing the web or researching a subject, avoid cluttering your desktop with multiple windows. You can instead view multiple web pages in a single Safari window by using tabs.
Preview a tab
In the Safari app
on your Mac, move the pointer over a tab.
Open a new tab
In the Safari app
on your Mac, click the New Tab button 
in the toolbar (or use the Touch Bar).To change the page that opens in new tabs, choose Safari > Preferences, click General, click the “New tabs open with” pop-up menu, then choose an option. See Change General preferences.
Open a page or PDF in a new tab
In the Safari app on your Mac, do any of the following:
Command-click a link on a page or a Favourites icon.
Command-click the Back button
or Forward button 
to open the previous or next page in a new tab.Type in the Smart Search field, then Command-click an item in the search suggestions, or press Command-Return.
Tip: To use these Command-key shortcuts to open pages in new windows instead of new tabs, choose Safari > Preferences, click Tabs, then deselect “⌘-click opens a link in a new tab.” See Change Tabs preferences.
Open a page in a new tab from the bookmarks sidebar
In the Safari app on your Mac, do any of the following:
Control-click a bookmark, then choose Open in New Tab from the shortcut menu.
Control-click a bookmarks folder, then choose Open in New Tabs.
Each bookmark in the folder opens in a new tab.
To open the bookmarks sidebar, click the Sidebar button 
in the toolbar, then click Bookmarks.
Open a tab in another window
In the Safari app
on your Mac, drag the tab over the desktop or choose Window > Move Tab to New Window.You can also drag the tab of one Safari window to the tab bar of another.
Note: Tabs in private windows can only be moved to other private windows. Tabs in non-private windows can only be moved to other non-private windows.
Automatically open pages in tabs
In the Safari app
on your Mac, choose Safari > Preferences, then click Tabs.Click the “Open pages in tabs instead of windows” pop-up menu, then choose an option:
Never: Links designed to open in new windows open in new windows.
Automatically: Links designed to open in new windows open in new tabs.
Always: All links designed to open in new windows open in new tabs, including links designed to open in specially formatted separate windows.
Reopen a recently closed tab
In the Safari app
on your Mac, choose History > Recently Closed, then choose the web page you want to reopen.You can also reopen a closed tab or window.