I read Chrome Frame closed last month, I thus tried to understand what it'd mean for the X-UA tag and after 3 hours of research I still didn't find the answer I'm looking for, my question is the following :
Is it still valid nowdays to use IE=edge,chrome=1 or should I stop at IE-edge from now on ? Or what would be the best pratice to do regarding X-UA, should it be avoided ?
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" /> serves two purposes.
IE=edge: specifies that IE should run in the highest mode available to that version of IE as opposed to a compatability mode; IE8 can support up to IE8 modes, IE9 can support up to IE9 modes, and so on.chrome=1: specifies that Google Chrome frame should start if the user has it installed
The IE=edge flag is still relevant for IE versions 10 and below. IE11 sets this mode as the default.
As for the chrome flag, you can leave it if your users still use Chrome Frame. Despite support and updates for Chrome Frame ending, one can still install and use the final release. If you remove the flag, Chrome Frame will not be activated when installed. For other users, chrome=1 will do nothing more than consume a few bytes of bandwidth.
I recommend you analyze your audience and see if their browsers prohibit any needed features and then decide. Perhaps it might be better to encourage them to use a more modern, evergreen browser.
Note, the W3C validator will flag chrome=1 as an error:
Error: A meta element with an http-equiv attribute whose value is
X-UA-Compatible must have a content attribute with the value IE=edge.
It's still valid to use IE=edge,chrome=1.
But, since the chrome frame project has been wound down the chrome=1 part is redundant for browsers that don't already have the chrome frame plug in installed.
I use the following for correctness nowadays
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<head>
<meta http-equiv='X-UA-Compatible' content='IE=edge'>
worked for me, to force IE to "snap out of compatibility mode" (so to speak), BUT that meta statement must appear IMMEDIATELY after the <head>, or it won't work!
来源：https://stackoverflow.com/questions/22059060/is-it-still-valid-to-use-ie-edge-chrome-1