Affecting showModalDialog() has been disabled in multi-process Firefox

Published: | Categories: DOM


The window.showModalDialog method has been unavailable when Firefox is running in the multi-process mode codenamed Electrolysis (e10s). At least Office 365 and Exchange 2016 were known to be broken due to an exception thrown by Firefox.

Because it’s technically difficult to support the functionality in e10s and the method has already been deprecated since Firefox 28, Firefox 46 hid showModalDialog from window rather than fixing the error. Office 365 and Exchange 2016 are now working again thanks to their feature detection.

Currently, e10s is enabled by default only on Firefox Nightly and Developer Edition. Once e10s is enabled on all Firefox channels in mid-2016, the method will no longer be available in Firefox.

Update: The method is no longer available on Firefox 48 and later as e10s has been enabled by default.