BerriAI/litellm · error · ValueError

Unknown extension for mime type: {mime_type}

Error message

Unknown extension for mime type: {mime_type}

What it means

Reverse-lookup failure in get_file_extension_from_mime_type: the supplied MIME type string does not match any entry in the FILE_MIME_TYPES mapping, so no canonical file extension exists for it. The mime_type argument is the invalid input.

Source

Thrown at litellm/types/files.py:161

        FileType.WAV: "audio/wav",
        FileType.WEBM: "video/webm",
        FileType.WEBP: "image/webp",
        FileType.WMV: "video/wmv",
        FileType.XLS: "application/vnd.ms-excel",
        FileType.XLSX: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
    }
)

"""
Util Functions
"""


def get_file_extension_from_mime_type(mime_type: str) -> str:
    for file_type, mime in FILE_MIME_TYPES.items():
        if mime.lower() == mime_type.lower():
            return FILE_EXTENSIONS[file_type][0]
    raise ValueError(f"Unknown extension for mime type: {mime_type}")


def get_file_type_from_extension(extension: str) -> FileType:
    for file_type, extensions in FILE_EXTENSIONS.items():
        if extension.lower() in extensions:
            return file_type

    raise ValueError(f"Unknown file type for extension: {extension}")


def get_file_extension_for_file_type(file_type: FileType) -> str:
    return FILE_EXTENSIONS[file_type][0]


def get_file_mime_type_for_file_type(file_type: FileType) -> str:
    return FILE_MIME_TYPES[file_type]

View on GitHub (pinned to 77b7c6c40c)

Solutions

1. Use a recognized MIME type (e.g. application/pdf, text/plain) or add a mapping for {mime_type}.
2. Pass an explicit file extension instead of relying on MIME type inference.

When it happens

Trigger: Thrown at litellm/types/files.py:161 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/499f3a16dc96f6b7. Report an issue: GitHub.