Windows error 14012 (ERROR_SXS_UNKNOWN_ENCODING

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The manifest specifies an unrecognized encoding group for side-by-side assembly data.

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ERROR_SXS_PROCESS_DEFAULT_ALREADY_SET	ERROR_SXS_UNKNOWN_ENCODING

ERROR_SXS_UNKNOWN_ENCODING_GROUP

ERROR_SXS_UNKNOWN_ENCODING_GROUP means that a side-by-side manifest or related data identifies an encoding group Windows does not recognize. The loader cannot interpret the affected manifest data reliably and stops activation-context generation.

What to check

Inspect the XML declaration and any generated manifest metadata for unsupported or misspelled encoding-group values.
Verify that build tools emit a normal supported XML encoding and that no post-processing step rewrites the declaration.
Compare the deployed manifest with the build output byte for byte if the issue appears only after installation.

Treat the encoding declaration as part of the manifest contract; changing text encoding without updating metadata can reproduce the failure.

Microsoft: assembly manifests

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