Unable to browse to a local website but browsing via IP works or from an external computer works. HTTP Error 401.1

If you are receiving a HTTP 401.1 error when browsing to a locally hosted website with a fully qualified domain name  (FQDN) or a custom host header and :

  • it works locally via IP,
  • it works from an external computer via IP,
  • it works from an external computer with a FQDN or a custom host header.

Then you should follow Microsoft support article 896861.

If it is a development environment it should be find to just disable to the loopback:

  1. Click Start, click Run, type regedit, and then click OK.
  2. In Registry Editor, locate and then click the following registry key:
    HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlLsa
  3. Right-click Lsa, point to New, and then click DWORD Value.
  4. Type DisableLoopbackCheck, and then press ENTER.
  5. Right-click DisableLoopbackCheck, and then click Modify.
  6. In the Value data box, type 1, and then click OK.
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