Multiple browser tabs sharing session by default
Normally browser such as IE, Firefox, if you open multiple tabs, all tabs share session cookies with the 1st opened tab.
I think this is simple to test, I think most of people know that .
However, if you want to see the official document about sharing session: please check here (from Microsoft IE blog)
In contrast, if you click New Window, New Tab, or Duplicate Tab on the File menu, or click on a desktop shortcut, the new tab or window will share session cookies with the original tab. This is called "session merging."