ERROR_SXS_XML_E_RESERVEDNAMESPACE - 14066 (0x36F2)
Manifest Parse Error : The namespace prefix is not allowed to start with the reserved string "xml".
Updated: Feb 21, 2026
Technical Meaning
The ERROR_SXS_XML_E_RESERVEDNAMESPACE error indicates a manifest parse failure. Specifically, it occurs when an XML namespace prefix is incorrectly used and starts with the reserved string 'xml'. This error suggests that there is a problem in the XML structure of a manifest file.
Error Details
This error code is part of the Windows Side-by-Side (SxS) assembly framework, which manages the deployment and execution of assemblies. The SxS framework relies on XML manifests to describe dependencies and other metadata for assemblies. When an invalid namespace prefix is encountered in these manifest files, this error is generated.
Usage Context
This error typically arises during the loading or processing of a manifest file by the Windows operating system. It could be triggered when attempting to load a .NET assembly or any other SxS assembly that relies on XML manifests for its configuration.
Developer Interpretation
Developers should interpret this error as an indication that there is a syntax issue in the XML manifest files being used. The specific cause of the error can be identified by examining the manifest file and ensuring that all namespace prefixes adhere to the correct naming conventions, particularly avoiding the use of 'xml' as a prefix.
Related Errors
ERROR_SXS_FILE_HASH(14059): A different hash value was found for an assembly.ERROR_SXS_MISMATCHED_PUBLICKEYTOKEN(14063): The public key token in the manifest does not match the expected value.
FAQ
Q: What causes this error?
A: This error is caused by using a namespace prefix that starts with 'xml' in an XML manifest file, which is reserved and not allowed.
Q: How can I resolve it?
A: Review and correct the XML manifest files to ensure that all namespace prefixes are correctly formatted and do not start with 'xml'.
Summary
The ERROR_SXS_XML_E_RESERVEDNAMESPACE error indicates a syntax issue in an XML manifest file, specifically related to the use of a reserved namespace prefix. Developers should carefully validate their manifest files to avoid this error.