IE11 - Webpage working with active developer tools… What are they doing?

Question

I have a web page here that is not working properly.

(It's the group manager plugin of the SCM-Manager, but that's an unimportant detail. If I try to add a group member, the member is not shown in the group.)

After some trial and error tests I made an strange discovery:

If the developer tools (F12) are open up meanwhile, everything works fine. There does not need to be any configuration changed and the webpage does not have to be reloaded. It just needs to have the developer tools opened up meanwhile...

My question is: What are the developer-tools doing (in the background?) when opened up, that makes the webpage working.

Some additional things you may should know:

• Our IE11 runs in compatibility mode (or "document mode" like MS calls it) for IE7 by default
• We use a so called "IE11epmode", with a file which includes exceptions for the compatibility mode and is located "C:\\ProgramData\\IE11epmode\\ie11.xml". I have already used this file several times to set the compatibility mode permanently (and not temporary like in the developer tools). This file gets rolled out in the company.
• When I was trying around, I found out: If I set in the developer tools the document mode to IE9 or higher it works fine. That's why I have inserted a compatibility rule for the webpage in the ie11.xml (mentioned above) to let the page run in "Edge"-compatibility. Now if I open up the developer tools, the document mode is "Edge" and also marked as default. (but it still does not work if the developer tools are not opened)
• If I choose in the developer tools the document mode IE8 or lower, I have the same effect as if the developer tools are closed (= webpage does not work)

I really hope you can help me!

Thank You & Best Regards

Lukas

Answer 1

If the webpage doesn't seem to be running in Edge mode with your current setup you could try inserting

<meta http-equiv="X-UA-Compatible" content="IE=edge" />

into the head.