When you open a link in a new tab with
target="_blank" like so:
Then the page that you open has access to the original page through
Window.opener. Depending on your case you may not want this. Actually I can’t think of a case where you do want the new tab to refer back to the opening tab.
Window.opener access use
At this moment, this is not available in IE or Edge, check out the caniuse site.
H/T Dillon HaferTweet