问题 In Firefox WebExtensions, how to know in which way is the new tab opened? By user click on the new tab button (+)? By User click on a link such as <a href="http://www.google.com/"> ? Note: I don't care if a new tab is opened by window.open() I found that, in callback of chrome.tabs.Tab.onCreated , there is a parameter passed in, assume it is named as firefoxTab : For tabs opened by click on +, its URL is about:newtab For tabs opened by click on <a href="" target="_blank"> , its URL is about