If a user is on your website and opens another link (also to your website) in a new tab, is it possible to differentiate this from the user just clicking on the link normall
It is client behaviour, so I think you could do something with javascript, like check for browser history, but it is ambiguous between a new tab and a new windows.
Beside that, not all browsers has tabs and not all browsers has the same meaning for what a tab is (in some are different process, in some others they aren't).
But, why would you want to check that? It really matter if your application is executing in a new tab or not? I don't think so...