Firefox gives you a preference so that when you click on a link that would normally open in a new window, it opens in a new tab instead. If you are using Safari, there is no such preference. You can end up with a lot of extra windows open as a result.

But Safari does have a hidden command line preference that lets you configure it so that links will open in new tabs instead of new windows. To set this up, do the following:

1 - Quit Safari.

2 - Open a Terminal window. If you don't normally using the Terminal application, you can find it in Applications -> Utilities.

3 - In the Terminal window, enter this command: defaults write com.apple.Safari TargetedClicksCreateTabs -bool true and then hit Enter.

You can then close the Terminal window and restart Safari. Now when you click on a link that would normally open in a new window, it will open in a new tab instead.

If you change your mind and you want the links to open in new windows again, just repeat the process but in the command in the terminal window change the true to false.