How long will IE compatibility modes work?

Question

Unfortunately, we have a massive legacy web application at work that we can't get rid of. It works on IE only, and is completely dependent on the "X-UA-Compatible: IE=EmulateIE8" to work correctly in newer IE versions.

My question is whether this is likely to one day suddenly stop working. I.e., will IE12 (or 13 or 14) come out one day and render the site useless because it doesn't bother with compatibility mode anymore?

If so, management won't want to hear it, but the sooner they do, the better.

Answer 1

As of IE11, document modes are deprecated but continue to work.

http://msdn.microsoft.com/en-us/library/ie/dn384051%28v=vs.85%29.aspx

I don't think they've decided (as of Jan 2014) exactly when it will be removed entirely (all at once in IE12 or gradually). Probably it depends on the amount of resistance people give to the deprecation status.

I also maintain a big internal application built between 2000-2004 or so. We have been banging the drum of needing to redo parts of the old site for years but new features are always priority. Personally I am bracing for hitting a brick wall with IE12 later this year, but hoping there will be a gradual removal.

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Edit: in early 2015 I've been reading that Windows 10 will ship with 2 browsers: code-name Spartan for the latest/greatest, and IE for legacy support. It's worth googling "Windows Edge" (formerly "Windows 10 Spartan") if you're interested in this topic. Possibly this is their answer for how to continue supporting older internal corporate web apps, without compromising the main consumer browser.

Hopefully the legacy browser doesn't fall behind the newer support, since our internal app is a mix of new and old web pages. It would suck if our company couldn't use the latest web technologies of 2016, 2017, etc., because older pages force our users to use the legacy browser. :(

Answer 2

Editor's Note: Microsoft has since announced that the official name for their new browser is "Microsoft Edge". Substitute it for any instance of [Project] Spartan that you see.

Powered by a new rendering engine, Spartan is designed for interoperability with the modern web. We’ve deliberately moved away from the versioned document modes historically used in Internet Explorer, and now use the same markup as other modern browsers. Spartan’s new rendering engine is designed to work with the way the web is written today.

The IE Dev Channel has a build you can use to test the new defaults. Here are the prerequisites:

• Windows 8.1 or Windows 7 SP1
• Internet Explorer 11
• Microsoft .NET Framework 4.0 (full version)
• PowerShell 3 (x86 or x64)

Here is the official recommendation:

Starting with IE11, document modes are considered deprecated and should no longer be used. Webpages that require legacy document modes to display properly should be rewritten to use features defined by modern standards. To learn more, see Compatibility changes in IE11.

References

• Project Spartan

• Compatibility changes in IE11

• Building a more Interoperable Web with Microsoft Edge

• Internet Explorer Developer Channel FAQ

• Announcing Internet Explorer Developer Channel

• Internet Explorer Developer Channel for Windows 7 SP1

• Internet Explorer Developer Channel for Windows 8.1