Open a New Tab
Press F12 to open Web Developer Tool
Open Console tab
Paste these code, and press ENTER to run:
chrome.tabs.query({}, function(tabs) { var firstSee = []; for (var i = 0; i < tabs.length; i++) { var url = tabs[i].url; var id = tabs[i].id; if (firstSee.indexOf(url) >= 0){ chrome.tabs.remove(id); } else{ firstSee.push(url); } } })
Bonus: you can create a Bookmarklet to do it:
javascript:chrome.tabs.query({}, function(tabs) {var firstSee = [];for (var i = 0; i < tabs.length; i++) {var url = tabs[i].url;var id = tabs[i].id;if (firstSee.indexOf(url) >= 0){chrome.tabs.remove(id);} else{firstSee.push(url);}}})
Then open a New Tab, click that Bookmarklet. Done!