Firefox to get Plugin Hang protection

Martin Brinkmann
Nov 27, 2012
Updated • Nov 30, 2012

I'm running the Firefox web browser without plugins, but I know many Internet users who are running ten or even more plugins at all times in the browser. Activities like watching videos on YouTube require plugins,  as Firefox is not yet supporting the H.264 format which is required to play back the videos not available in WebM format on the site.

My two main concerns with plugins are stability and security. Security updates are released regularly for plugins such as Adobe Flash Player or Java but it is still up to the user to install those updates the moment they come out. That, and the fact that companies like Adobe have failed to produce a working update system that does so are the main reason why many Internet users are running outdated and often insecure plugins in their web browser. This can be partially mitigated by installing a security add-on like NoScript in the browser which blocks automatic plugin execution on all websites you visit.

Stability is the other concern. Plugins may become unresponsive which sometimes requires you to restart the browser to continue working. In any event, you may wait a preset amount of time, currently set to 45 seconds, before Firefox kills the non-responding plugin so that you can keep on working with the browser.

Firefox's new Plugin Hang protection feature displays information about what is happening in the background to you to give you control over the next step.

warning unresponsive plugin

It provides you with the option to stop the plugin right at that point in time, or wait and see if the plugin recovers. What's interesting here is that you are also informed which plugin caused the issue in the browser. Stopping the plugin will kill it but won't affect the underlying browser, provided that out of process plugins are used.

The feature is currently only planned for desktop versions of Firefox on Windows. You will note that a child process is created, plugin-hang-ui.exe which is used to display the dialog box to you when plugins hang in the web browser.

Several preferences are available that help you customize the feature:

  • dom.ipc.plugins.hangUITimeoutSecs - The number of seconds that Firefox waits after a hung plugin has been detected before the notification is displayed on the screen. A setting of 0 disables the feature.
  • dom.ipc.plugins.timeoutSecs - This preference changes slightly. It determines the number of seconds that Firefox waits before a plugin gets killed automatically. Instead of starting the countdown right away, it is now started after the notification is displayed.
  • dom.ipc.plugins.hangUIMinDisplaySecs - the minimum number of seconds that Firefox should display the notification on the screen.

The release target for the Plugin Hang UI is Firefox 19 which will come out on 19.2.2013 if everything goes according to plan. (via Techdows)


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  1. Narisi said on December 4, 2012 at 8:03 am

    “Docs Online Viewer”
    userscript or firefox extension links all online documents and files to be opened with Google docs. It is my way to avoid nasty Adobe reader plugin. It is fast and light weight and opens documents similar to opening other webpages.
    Docs Online Viewer Links:
    Firefox Addon:
    Home Page:

  2. Candle said on November 28, 2012 at 12:04 pm

    “Security updates are released regularly for plugins such as Adobe Flash Player or Java but it is still up to the user to install those updates the moment they come out. That, and the fact that companies like Adobe have failed to produce a working update system”

    With regards to Flash how is this statement correct? Adobe Flash Player has had the ability of automatically updating w/o user intervention for months now.

    1. Martin Brinkmann said on November 28, 2012 at 2:46 pm

      But the updates are not immediate usually.

  3. Transcontinental said on November 27, 2012 at 3:15 pm

    Indeed Firefox’s new Plugin Hang protection will be an excellent initiative particularly for users (as some of my relatives) who have a long list of Firefox plug-ins and worse, seem not to give the slightest attention to it.

    As many others and here as well perhaps, I dislike what is not required and look forwards accordingly to know what’s running. Only 2 plug-ins here, and 3 off (deactivated):

    Shockwave Flash
    Microsoft® Windows Media Player Firefox Plugin

    Microsoft® DRM (Off)
    Microsoft® DRM (Off)
    Windows Media Player Plug-in Dybamic Link Library (Off)

    PDF calls Foxit Reader which is not set to open in browsers, but for non-private data I use a userscript called Docs Online Viewer

    Everything is rolling fine. No need for an armada of plug-ins unless absolutely required (and/or truly wished). Making it compact is a relief for the application, for the OS, for the user’s mind.

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