IE11 Enterprise Mode and Compatibility View are Additive, not Exclusive

It’s been a busy couple of months in the world of app compat, so I’ve got a backlog of things to cover.

Let’s start with an FAQ that I’ve gotten in nearly every conversation I’ve had about web app compat since April.

On April 8, we introduced a feature called Enterprise Mode. This is a feature designed specifically to help customers who are on Windows 7 but still using the oldest version of IE available on that platform (IE8).

The engineering work behind this was really a thing of beauty. Yes, it seems an obvious feature now, but a year ago it wasn’t even an idea. In fact, a year ago, I was on a plane to Japan to start the initial visits to try and figure out what we needed to build to make things easier, because we knew they were too hard. Then, we had a “One Microsoft” symphony to produce software. Consulting and Support came together with Marketing and Engineering to represent everyone’s feedback, to run a rapid beta program, and to deliver a product in just a few months. This truly is a feature designed by and for the enterprise, with a 360 degree perspective on web app compat. Easily the most collaborate project I’ve worked on at Microsoft, and if this is indicative of what we can expect in the new Microsoft, we’re in for a lot of goodness.

What emerged is a high-fidelity emulation of IE8 – better than anything we’ve done before. Now, specifically, our goal wasn’t to make the emulation one that couldn’t be defeated. Rather, it was to make emulation that worked on enterprise apps that actually already existed in the wild. So, for folks who try to foil it and come up with something that breaks it, you an absolutely succeed (and I can definitely show you a few ways). But, here’s the thing – we chose not to care about potential bugs (unless they had a demonstrable likelihood of existing) but on actual bugs that exist in the real world. And the outcome of the beta is that we achieved that, but it also indicated that we were likely to run across more actual bugs, and we’re prepared for that.

After that long intro, here’s the part that people are getting hung up on…

Enterprise Mode does NOT replace Compatibility View.

That bears repeating – Enterprise Mode does not replace Compatibility View. They seem really similar, and plenty of folks call Compatibility View “Compatibility Mode” so they sound even more similar. But they’re actually additive.

As emulation of IE8, we have to include everything that IE8 had in it. And IE8 is the version that first introduced Compatibility View. So, if Enterprise Mode didn’t contain Compatibility View, it wouldn’t be a high fidelity emulator!

So, when in Enterprise Mode, you may have to fiddle around with Compat View also!

Given that, here is the approach that I normally recommend when it comes to quickly testing and assessing web app compat for a migration to IE11:

  1. Just trying running it on IE11 to see if it works – there’s a reasonable chance that it will
  2. If it doesn’t work on IE11 natively, try enabling Enterprise Mode
  3. If it doesn’t work in Enterprise Mode, try modifying the Compatibility View setting (to the opposite of what it currently is)

If none of those work, you can assign it to a technical team for exploration of other document modes or configurations before diving into the code and troubleshooting, but most customers find that this clears away nearly everything, so that if there is anything that requires special attention it’s not surrounded by noise and the ambiguity that a long list of “I don’t know” apps brings.

Another conversation this normally leads into is “wow, Enterprise Mode is way easier and more powerful to manage using group policies than Compat View was, do the changes apply to compat view also?” The good news is that we didn’t make things any worse – it’s just as manageable as it has been since IE8. The bad news is that we didn’t make things any better (and the question implies that it’s not good enough, as do the inevitable sighs). But we’ve definitely heard the feedback that this is an experience folks would like to see improved!

Comments (22)

  1. Neil Soiffer says:

    Enterprise mode is a great idea, but unfortunately it is buggy for binary behaviors. My company makes MathPlayer, a free plug-in to IE. It is (was) the most complete implementation of MathML available. MathPlayer works with screen readers and other assistive technology to make the math accessible in IE. That all died with with IE11. Enterprise mode would resurrect math accessibility in IE if you fixed the existing bug (…/crash-in-enterprise-mode-with-binary-behavior). The bug causes IE11 to crash in enterprise mode; IE8 works fine on the same (and similar pages) with MathPlayer.

    You'll find a number of people commenting on the death of math accessibility in IE on the feedback pages. If you fix the bug, the accessibility community would be very grateful. Access to math is a huge problem. IE used to have the best math accessibility available and it can have that once again if the bug is fixed.

  2. SJB says:

    This is interesting timing, since we have a premier support call open at the moment about an app that doesn't work under IE11 Enterprise Mode.  I was all excited for a few minutes thinking the flip compatibility mode might be the extra tweak needed,

    anyway, in our experience Enterprise Mode has been fantastic, and solved all but one of our app issues.  For that I extend my thanks to all those that made it happen.  

  3. cjacks says:

    @Neil – we have a bug open on this and added your details to it.

  4. DonPick says:


    3.If it doesn’t work in Enterprise Mode, try modifying the Compatibility View setting (to the opposite of what it currently is)

    By this, do you mean "If CV is on, try it with CV off. If CV is off, try it with CV on" ?

  5. DonPick says:

    Hi Chris, there are several forum discussions (and probably lots of email in your inbox 🙂 about enterprises trying to understand the CV vs. EM manageability methods, but in particular, one which seems confusing is "how do CV and/or EM settings & sitelists work, for roaming users?)

    This thread:…/emie-remote-desktop-services-with-mandatory-profile suggests that either we aren't doing it right, or, we're assuming a feature exists (but it doesn't exist?) to cater for "roaming" users.

  6. cjacks says:

    @DonPick – Yes, that's precisely what I mean with regards to inverting CV settings. And as for locally applied enterprise mode options and their ability to roam – this feature is something we designed to facilitate testing and crowd sourcing, and not as an end user solution, so we didn't validate it in all of the production scenarios that might exist. The XML site list should, however, work in such scenarios.

  7. PM says:

    Hi Chris,

    from the content of the post it is not clear to me if there is any difference between IE 11 with CV on and EM on as compared to IE11 with CV on and EM off.

    The answer to this question makes a big difference to the possible combinations that I have to test for an application which is not running properly in IE 11. If it makes no difference, I can run the test once (either CV+EM or CV alone), if it makes a difference, I have to test both.  

  8. cjacks says:

    PM – CV is even more compatible with EM on than it is with EM off – we disable some perf enhancements and bring back some capabilities which were deprecated in IE11 with EM off, so definitely good to work the process. You should start with standard IE11 with the same setting you were historically using (CV on or off as it was on actual IE8) and then EM if that doesn't succeed for you, to increase the compatibility of CV.

  9. Glenn Mantle says:

    What are our options on IE11 if a site works with IE9 but not IE8.

  10. cjacks says:

    Glenn – today, your best bet is to leverage X-UA-Compatible to choose the document mode that works (which I'm guessing is IE9) assuming it has been verified not to work in a newer document mode (such as IE10 or IE11 / Edge). We're looking at ways to make this easier to configure without touching the web server to add this header, but today that's your best bet.

  11. Sean Lillis says:

    Hi Chris,

    Based on your comments above there are 4 basic scenarios for testing compatibility in this order:

    1. Native Mode (IE11)

    2. Native Mode + CV (IE8 + performance enhancements and some legacy capabilities removed)

    3. Enterprise Mode (IE8)

    4. Enterprise Mode + CV (IE8 plus Compat View (IE7))

    Does this order look right? I've added in brackets what I think each scenario maps to in terms of equivalent browser functionality to try to simplify this for testers, although obviously these are generalisations. We are considering leaving out step 2 to try to streamline the testing approach as appears to be the recommendation in the original blog post.


  12. cjacks says:

    Sean – I outline the steps I typically see here:…/enterprise-conversations-on-internet-explorer-support-changes.aspx

    The only real difference is that I don't disable or enable CV (your steps 1 and 2) but just leave it the same and move to Enterprise Mode as step 2. But you can absolutely leave the step in if you're interested in knowing. (I think it's also interesting in understanding how far back you have to go if IE11 document mode doesn't work, but that takes even more steps and more expertise – it all depends on how much time you have and how much knowledge you want to pull out to drive future initiatives.)

  13. Marie Claude says:

    Hi Chris,

    I have a question on the best way to use CV and/or EM.

    We have some Corporate applications that don't work properly with IE11. We have used CV and added our domain (* in the list. We still have issues on some of these apps.

    In EM, we can add a website (as

    Should we still enable CV and add the website in EM in addition? What mode will "" use? EM or CV?…

    Thanks for your answer.

  14. cjacks says:

    Hi Marie,

    Yes, if you need CV in IE8, you'll still need it in EM. They are additive, and not exclusive.

  15. Marek says:

    Is it possible to define local files (html) for EM? My application has all files on the local file system: c:myappindex.html. The app works with CV    

  16. cjacks says:

    Hi Marek – we don't support local files in EM – is it not possible to add X-UA-Compatible or simply continue to leverage CV? Help me understand the app a little better.

  17. Marek says:

    In my previous post I should say that the application works with "X-UA-Compatible" (have not tried the CV as it probably does not work with local files). Is the EM equivalent to X-UA-Compatible?    

  18. Geoffrey Beaston says:

    My Company is in the middle of testing to ensure all our Apps work correctly in EM, however we have an app that the vendor has not yet upgraded and still only officially supports IE7. This app works in IE8 with only one issue that is able to be dealt with, however in EM there is a page that when it opens freezes the IE session completely. This is not the same location of the app where the other issue exists. Any ideas how to make it work?

  19. cjacks says:

    @Marek – if it works with X-UA-Compatible, then I would continue using that.

  20. cjacks says:

    @Geoffrey – Are you familiar with the F12 tools? I would try the various document modes and see if one works.

  21. Developer@xyz says:

    Hi Chris,

    We have a legacy application with different pages rendering in different compatibility view .

    What would the approach you would suggest for checking app compatibility for IE 11.

    Application currently works in CV for older version of browser.

  22. Todd says:

    Hello Chris,

    I am an IT Project Manager, and I am implementing two hosted software applications for our Community Development Department. One application syncs with the other. Both are on the same server with the same domain but with different threads.

    The problem is that one application requires Compatibility View in IE 11, but the other does not. And since CV won’t differentiate two separate addresses from the same server (it always defaults to just the domain), the setting confuses the second application into believing that it too, is set up with CV. The result is one malfunctioning application. Turn CV completely off, and the other application won’t function properly.

    Why won’t the CV dialog differentiate two separate web addresses from the same server???

    We are going live in a week and any help or solutions would be very much appreciated.

    Thank You!

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