Add-ons that intercept the WM_CLOSE message may fail in Internet Explorer 9 later versions

This article provides information about resolving the issue that a browser tab or window can't be prevented from closing by the WM_CLOSE message intercepted by some add-ons in Internet Explorer 9 or a later version.

Original product version:   Internet Explorer 9 and later versions
Original KB number:   2587178

Symptoms

Some add-ons for Internet Explorer attempt to prevent a browser tab or window from closing by intercepting the WM_CLOSE message before the tab receives it. In Internet Explorer 9 or a later version, this action may not prevent the tab from closing.

Cause

Internet Explorer 9 or a later version, like Internet Explorer 8, isolates tabs to their own processes. When a tab is closed in Internet Explorer 8, the underlying tab process must first close before the tab visually disappears. To make Internet Explorer 9 or a later version more responsive to the user, the browser will now hide a tab as soon as the user closes it. Internet Explorer 9 or a later version will handle much of the mechanics of closing a tab or window while the tab is invisible.

Resolution

Intercepting or hooking the WM_CLOSE message is not a supported method of preventing a tab in Internet Explorer from closing.

However, the author of the add-in or of the web pages may be able to make changes that allow this method to work in Internet Explorer 9 or a later version. This new tab close behavior will not be used if the window.onbeforeunload event has any registered handlers. The following code is an example of this approach, as it might be implemented in script on the page:

function myHandler()
{
 // do nothing
}
window.onbeforeunload = myHandler;

More information

For more information about Internet Explorer, see Internet Explorer help.