IIS 10 not serving (404.7) default document with File Name Extensions enabled

If you disable Allow unlisted file name extensions in IIS using the Request Filtering module you’ve always had to then allow “.” (just a period by itself) in the File Name Extensions to then allow IIS to feed up the default document without it being in the URL.  For example http://www.google.com versus http://www.google.com/index.htm which without the . added won’t work.  In IIS 10 on a couple of websites we found they would throw 404.7 errors when this was configured even with the . in the allow list.

On these websites we had to go into the Default Document portion of the website and ensure the item that is the root default document of the website is at the top of the list.  This was never an issue in previous IIS versions and the root default document could be anywhere in the list.

Example that worked for http://www.website.com/default.htm on all previous versions of IIS

  • index.htm
  • index.html
  • default.htm
  • default.aspx

What we found was required for IIS 10 to get http://www.website.com/default.htm to load without 404.7 error

  • default.htm
  • index.htm
  • index.html
  • default.aspx

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