Go to about:config and check browser.tabs.closeTabByDblclick.

You can also close a tab via a middle-click with the mouse scroll wheel.

• https://support.mozilla.org/en-US/kb/mouse-shortcuts-perform-common-tasks
• https://support.mozilla.org/en-US/kb/keyboard-shortcuts-perform-firefox-tasks-quickly

Yes mate that is what i always did and it is not working for some reason. The value is set to "true".

I'm using middle button at the moment but it is just hard to get used to it.

It is weird that on other computers everything is working fine after udating firefox, but on this one it doesn't after fresh install.

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.

• switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems