What does Windows error code 15101 (ERROR_MUI_INVALID_FILE) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The MUI resource file failed validation and could not be loaded.

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ERROR_MUI_FILE_NOT_FOUND	ERROR_MUI_INVALID_RC_CONFIG

ERROR_MUI_INVALID_FILE

ERROR_MUI_INVALID_FILE means Windows rejected a language-specific .mui resource file during validation. A MUI deployment pairs language-neutral application code with language-specific resources; the loader validates their association before loading the resource file.

Compare the .mui file with the exact language-neutral binary it was built for, including version and deployment path. Mixing resource files from another build can fail validation even when the MUI file is structurally readable.

What to check

Confirm that the .mui file was deployed with the language-neutral executable or DLL from the same build.
Check that the language folder and file name follow the MUI layout expected for the associated language-neutral file.
Rebuild and redeploy the resource file instead of copying a .mui file from a different product version.

Microsoft: MUI Resource Management

Microsoft: Deploying multilingual resources

Microsoft: About Multilingual User Interface

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