I am tried to log in to web application inside the server , but I can't to login although I am sure the username and password is correct

I asked someone who tells me disable the loopback check, but I don't know what is this loop back? what is the useful of loopback check and how I can disable it ?


3 Answers 3


Disabling Loop backcheck is commonly used practice in lower envirnoment i.e Dev and QA but in Production it is depend.

Windows Server 2003 SP1 introduced a loopback security check. This feature is obviously also present in Windows Server 2008. The feature prevents access to a web application using a fully qualified domain name (FQDN) if an attempt to access it takes place from a machine that hosts that application. The end result is a 401.1 Access Denied from the web server and a logon failure in the event log.

Read this blog to completely understand the issue

You can disable it using the following method:

To set the DisableLoopbackCheck registry key, follow these steps:

  1. Set the DisableStrictNameChecking registry entry to 1. For more information about how to do this, click the following article number to view the article in the Microsoft Knowledge Base: 281308 Connecting to SMB share on a Windows 2000-based computer or a Windows Server 2003-based computer may not work with an alias name
  2. Click Start, click Run, type regedit, and then click OK.
  3. In Registry Editor, locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
  4. Right-click Lsa, point to New, and then click DWORD Value.
  5. Type DisableLoopbackCheck, and then press ENTER.
  6. Right-click DisableLoopbackCheck, and then click Modify.
  7. In the Value data box, type 1, and then click OK.
  8. Quit Registry Editor, and then restart your computer.

Read more about above steps over here

  • Thanks for quick reply, but what do you mean with in production is depend? Oct 25, 2016 at 21:48
  • read the 1st link i mentioned, "However, for production environments, DO NOT DISABLE this feature. You are unpicking a serious security check of the OS. If that environment underwent a security audit by a competent security engineer, it would be flagged."
    – Waqas Sarwar MVP
    Oct 25, 2016 at 21:50

Yes he is right, you should disable loopback check on the server

Regarding what is this loop back? and what is the useful of loopback check ?

a loopback security check: is a feature that prevents access to a web application using a fully qualified domain name (FQDN) if an attempt to access it takes place from a machine that hosts that application. For more details check DisableLoopbackCheck & SharePoint

Regarding How I can disable it ?

  • Open Regisrty by Running Regedit.msc at run dialog.
  • Navigate to HKEY_LOCAL_MACHINE > System > Control > Lsa .
  • Right Click on Lsa to add a new key.
  • Rename key with DisableLoopbackCheck > Right-click on it > select Edit.
  • Change value data from 0 to 1 > click OK.
  • Try now to login that should be worked .!

For more details with image check Configuring Alternate Access Mapping inside SharePoint Server 2013


Here's a link that tells what it is and how to disable it.disableloopback check link Spence Harbar is a genius.

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