Dual engine advantage: Legacy sites and Microsoft Edge
Published Feb 04 2021 04:35 PM 18.4K Views

Update June 21, 2021 – This blog post has been edited to reflect additional resources relating to App Assure and Microsoft Edge. Please visit the bottom of this page to see more.


The App Assure service launched in October 2018, reassuring our customers that their applications will work on the latest versions of our software, and if they experience any issues, we’ll help them fix them at no cost! Since then, we’ve helped Windows 10 (x86, x64, ARM64), Microsoft 365 Apps, Microsoft Edge, and Azure Virtual Desktop customers address application compatibility issues, so that they can continue to use their business critical applicationsThis is included at no additional cost as part of the FastTrack benefit, eligible with Microsoft 365 and Windows 10 plans of 150+ licenses. 





A year ago, App Assure started assisting with Microsoft Edge-related cases and through our customer engagements, weve found that the most successful customers followed our recommended deployment process for Microsoft Edge. Using Enterprise Site Discovery to identify legacy sites and apps helps admins gain insights and make informed decisions when configuring Microsoft Edge. We highly recommend understanding your environment and what sites need Internet Explorer (IE11 and can use IE mode in Microsoft Edge. 


What is Internet Explorer mode?  

IE mode enables legacy apps and sites to work in Microsoft Edge. Microsoft Edge supports modern apps, thanks to the Chromium engine, and legacy apps, thanks to IE mode utilizing the MSHTML engine. Some legacy apps use ActiveX controls (e.g., Java, Silverlight), Browser Helper Objects, etc. that are not supported natively by the Chromium engine and, therefore, may not run properly without setting up IE mode in Microsoft Edge


IE mode: 

  • Makes it easy to access the legacy sites that your organization needs in a single browser 
  • Gives your team more time to upgrade legacy apps to faster, more modern technology 
  • Enables automatic switching from the Microsoft Edge engine to the IE engine for sites that need it 

We understand how critical legacy web apps can be to enterprises. Since we started supporting Microsoft Edge, we’ve discovered that many compatibility issues fall into two main categories that the Microsoft Edge built-in browser features mitigate. Here are two of the most important steps that will keep your legacy apps working smoothly as you plan for and deploy Microsoft Edge:


1. Perform Enterprise Site Discovery  

  • Discover which sites are using legacy document modes 
    • Unless these sites are detecting modern browsers and providing different HTML, they will likely need to run in IE mode 
  • Discover which sites are using ActiveX controls 
    • Modern browsers including Microsoft Edge don’t support ActiveX controls; unless these sites are detecting modern browsers and providing different HTML, they probably need to use IE mode

2. Identify and configure neutral sites for authentication/SSO 

  • Identify SSO authentication servers and configure them as neutral sites

    • If you navigate to a sign-on server from Microsoft Edge, then you want to stay in Microsoft Edge to authenticate 
    • If you navigate to a sign-on server in Internet Explorer mode, then you want to stay in Internet Explorer mode to authenticate 


Common symptoms of legacy sites on modern browsers and how to fix them 

There are some common symptoms you may experience and options that most likely resolve them. The symptoms below may indicate the site has legacy components and the issue will likely be resolved by configuring IE mode or neutral sites.


Web app or site functionality is impaired or missing 
  • The browser displays a white screen instead of rendering the content 

  • Buttons are missing or don’t perform the expected outputs when clicked 

  • Expected fields are blank or not interactive 

  • “Unsupported Browser” or similar messaging appears 

  • Displayed content is misaligned 

As of Microsoft Edge version 86, you can quickly test the site in IE mode by enabling the policy to 'Open sites in Internet Explorer mode' under 'More Tools' to determine if adding the URL to your site list will resolve the issue. Using the built-in F12 Developer Tools to inspect the site code can help determine if a compatibility Document Mode is being specified, which you can then config in your site list. As noted earlier most, if not all, of these sites would be identified by following Enterprise Site Discovery. So, it might be worthwhile to go back and run it for the rest of your site inventory.


Authentication / Single Sign-On issues 

  • The site list has been configured, but users are being prompted for credentials after an app or site opens in IE mode 

  • The authentication process goes into a loop, hangs, or fails  

  • “500 Internal Server Error” is displayed 

  • SAML Bad Authentication Error 400 is displayed  

These issues are most commonly due to sites in IE mode redirecting between IE and Microsoft EdgeResolve these quickly by configuring the URL as a neutral site in the Enterprise Site List. Once the authentication sites are configured as neutral sites, the authentication credentials will flow seamlessly between modes.


Need Microsoft Edge deployment assistance? 

To assist you as you deploy Microsoft Edge, Microsoft FastTrack  is equipped with experts to help you work through the above-mentioned deployment items like Enterprise Site Discovery, IE mode configuration, and other deployment-related activities. This is included at no additional cost as part of the FastTrack benefit, eligible with Microsoft 365 and Windows 10 plans of 150+ licenses. 


Need help with your applications? 

If you’ve tried the suggested remediations above and are still having concerns with your app on Microsoft Edge, App Assure is ready to help. If your app or site works with Internet Explorer 11, supported versions of Google Chrome, or any version of Microsoft Edge, App Assure will help you get them working in Microsoft Edge, at no additional cost with eligible Microsoft 365 and Windows 10 plans of 150+ licenses.


Visit the App Assure page and sign in to submit your request for assistance for a dedicated App Assure ManagerIf you experience any issues submitting a request for assistance, please contact ACHELP@microsoft.com and our team members will reach out to you to help! Learn more about App Assure compatibility assistance for Microsoft Edge here. 


Additional App Assure and Microsoft Edge resources, as of April 6, 2021

For more information, please watch these two videos:

Bring your apps to Microsoft Edge with App Assure: Hear tips and tricks

Internet Explorer mode and compatibility in Microsoft Edge


The future of Internet Explorer is in Microsoft Edge, as of June 21, 2021

On May 19, 2021, Microsoft announced Internet Explorer’s retirement will come in June 2022, and that the future is in Microsoft Edge. In summary, Microsoft Edge benefits include:

  • A faster, more secure and more modern browsing experience
  • Streamlined productivity
  • Compatibility with older, legacy applications and websites thanks to Internet Explorer mode (“IE mode”)

For full details, please refer to:

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‎Jun 21 2021 01:04 PM
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