Enterprise Mode is an option Microsoft has made available in Internet Explorer 11 that allows you to load webpages using a modified browser configuration that emulates IE8. This is a valuable tool when you need to (and should) upgrade to the latest versions of IE but have legacy web apps or other websites that may not be fully compatible. I am not going to cover how to enable Enterprise Mode but it’s quite simple (Here is a good place to start). You can either enable through Group Policy (or LocalGPO on non-domain computers) or enable via registry setting on individual computers. You can also configure logging to capture when users turn on/off Enterprise Mode, and even publish a site list to have specific sites default to Enterprise Mode when opened. Once enabled the user can turn on Enterprise Mode (per site) directly from the Tools menu.
We enabled Enterprise Mode through Group Policy to make the option available for users as they migrate to IE11. Our testing and pilot users all reported success as the Enterprise Mode option appeared in the Tools menu as it should. However, soon after we deployed the GPO company wide we had reports of the option not show up for some users. Then after several days the Enterprise Mode option would suddenly appear. We performed the standard troubleshooting and highly suspected a GPO issue. Unfortunately we found the GPO was applying properly to the workstation and everything else checked out ok.
After further testing we solved the mystery. Why wasn’t Enterprise Mode showing up in IE? well… Microsoft neglected to tell anyone that Enterprise Mode is only supported in specific IE11 builds. And of course, the version (11.0.9600.16672, Update versions: 11.0.10 KB2963952) in our base image is not supported. The GPO had applied but the option would not be available in IE until Internet Explorer was brought to a supported level. It all makes sense now. When a new workstation was deployed the version of IE11 did not support Enterprise Mode, but then as software updates were applied through SCCM the latest version of IE11 was installed and the option was made available.
Update 08/14/2015: Microsoft released the Enterprise Mode update on April 8th, 2014 with Cumulative Update KB2929437. This means the supported IE11 browser version is 11.0.9600.17041 and above.