Mozilla has added plugin Hang UI for Windows in Firefox 20 which appears and allows the user to terminate not responding plugins like Flash before Firefox killing it after waiting for preset time 45 seconds.

Reason for Mozilla to create Plugin Hang UI: Firefox with Out-of-Process Plugin architecture automatically kills unresponsive plugin after waiting for 45 seconds. During this time, hanging plugin locks Firefox main process and makes it not responsive. 

When Flash plugin hangs this Plugin Hang UI will be invoked after 11 seconds and a child process plugin-hang-ui.exe being created which shows the UI with following message.

“shockwave Flash may be busy, or it may have stopped responding. You can stop the plugin now, or you can continue to see if plugin will complete”.

User can kill the plugin straight away without having to wait for browser to terminate it by clicking on “stop plugin” button on UI. Or he can click on “continue” button on Plugin Hang UI where Firefox eventually kills the unresponsive plugin after 45 seconds.

Plugin Hang UI showing unresponsive warning dialog in Firefox 20

Disabling Plugin Hang UI and Plugin Hang UI.exe process in Firefox

This UI has been turned out to be annoyance for some users we’ve came to know this through comments. To disable plugin hang UI and its executable process (which appears running in task manager) that invokes the UI

1.Visit about:config and click on “I’ll be careful , I Promise!”

2. Find the following preference and and set its value to ‘0’ (zero).


3. From now onwards Plugin Hang UI won’t appears in future, you can find this process as something similar to disabling plugin-container.exe.

Reproducing Plugin Hang UI can’t be possible? have you encountered Plugin Hang UI? have you found it annoying? share your thoughts with us in comments.