Tap here to go to the mobile version of the site.
Your Firefox is out of date and may contain a security risk! Upgrade Firefox

Support Forum

Firefox warns about closing tab so as not to loose the content, can I disable this?


I have various browsing sessions, one is for email, one for studies etc. With one of the browsing sessions when I try to close a tab, firefox asks if I really want to close this tab, because for some reason it thinks I'm writing a message. This is really starting to get on my nerve, not because of firefox, but because of the website that triggers these popups.

Is there a way to disable these?

I've trying so hard to find an answer, so I would be really grateful for your help!

Blessings, Janne

Additional System Details

Installed Plug-ins

  • Next Generation Java Plug-in 10.11.2 for Mozilla browsers
  • Shockwave Flash 11.5 r502
  • VLC media player Web Plugin 2.0.2
  • Facebook Video Calling Plugin
  • Google Update
  • Adobe PDF Plug-In For Firefox and Netscape "9.5.2"
  • 4.1.10329.0
  • DivX Web Player version
  • DivX OVS Helper Plug-in
  • Wacom Dynamic Link Library


  • User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:18.0) Gecko/20100101 Firefox/18.0

More Information

  • Top 10 Contributor
  • Moderator
10749 solutions 96724 answers

That is caused by a script that run on the page and is triggered by an onbeforeunload event

You probably can't disable such a warning alert, but you can check if you can find a Greasemonkey script to disable such an event

  • void(onbeforeunload = null);
finitarry 157 solutions 2175 answers

Years before, I set up a setting to block onunload from opening popup windows on some advice from a website.

user_pref("dom.disable_window_onunload", true);
Will that still work with the current release of Firefox?  If not, will this work?
user_pref("capability.policy.default.Window.onunload", "noAccess");