I had an application that was running with HTTP in all the browsers with no problem. Then I configured an Let's Encrypt SSL certificate using win-acme v1.9.10.1. Find the link below: https://github.com/PKISharp/win-acme/releases/tag/v1.9.10.1

After installing the certificate, I was able to run my application with HTTPS on all browsers ( Chrome, Firefox and Microsoft Edge) expect IE 11.

This is what's displayed when I try to run my application on IE 11:


What could be causing this issue? Is IE 11 supported by Let's Encrypt? Thanks.

PS: The content above my DOCTYPE tag isn't part of my code.

  • Hi, does you got a certificate error in IE11 (red warning or such) ? as I think it's an application error more with the backend more than a lets's encrypt's error – yagmoth555 Aug 1 '19 at 13:53
  • I don't have any certificate error in IE11. Here's an article from Microsoft Support: support.microsoft.com/en-ca/help/3151631/… but since it's working on Microsoft Edge, it doesn't explain why it's not working on IE 11. I also don't think that it's a Let's Encrypt error,but I'm not able to say what could be causing the issue. @yagmoth555 – LuVu Aug 1 '19 at 14:26
  • Do a simple test, put a static web page (.html) and naviguate to it in IE 11, if ok and no error, then I would check the app if you can debug what it send. At this point I'am not a dev, but maybe add logging to file to trace back where the apps fail to send the content – yagmoth555 Aug 1 '19 at 14:38

Is IE 11 supported by Let's Encrypt? Support depends more on the operating system than the browser. If you are using latest version of Windows everything should be fine: https://community.letsencrypt.org/t/which-browsers-and-operating-systems-support-lets-encrypt/4394

I suggest you to make full validation of configuration and find anything suspicious: https://github.com/PKISharp/win-acme/wiki/Validation-issues

Standard things to check on the browser side:

  • Do other sites with the Let's Encrypt certificate work in IE11?

  • Does the website work on other computers with IE11?

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