You cannot post data to a non-NTLM-authenticated Web site

Applies to: Internet Explorer 11

Important This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows Registry


You cannot post any data to non-NTLM authenticated Web sites.


This issue can occur after you visit an NTLM authenticated folder.

Note Microsoft Internet Explorer requires NTLM authentication for all visits after you visit one NTLM authenticated folder.


Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To resolve this issue from the client side, use Registry Editor (Regedt32.exe) to add a value to the following registry key:
HKEY_CURRENT_USER/Software/Microsoft/Windows/CurrentVersion/Internet Settings/
Note The above registry key is one path; it has been wrapped for readability.

Add the following registry value:
Value Name: DisableNTLMPreAuth
Data Type: REG_DWORD
Value: 1

More Information

NTLM Pre-authentication is an optimization, it allows Internet Explorer to send the initial NTLM handshake proactively if the same server has already challenged Internet Explorer for NTLM authentication in the present browsing session. NTLM Pre-authentication is performed in every new TCP connection established with the server.

When a POST request is being sent in a new TCP connection, Internet Explorer will perform NTLM Pre-authentication and exclude the POST request payload and content length, because they aren't required to complete NTLM authentication successfully. At this point, if the server doesn’t challenge Internet Explorer for authentication but instead expects the POST request payload to be delivered, the underlying web application may not work as expected.

When the server challenges Internet Explorer for authentication, disabling NTLM Pre-authentication won't affect the Internet Explorer’s ability to authenticate with NTLM.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.