XLC
application/vnd.ms-excel
Magic Bytes
Offset: 2080
4D 69 63 72 6F 73 6F 66 74 20 45 78 63 65 6C 20 35 2E 30 20 57 6F 72 6B 73 68 65 65 74
XLC is a legacy file format developed by Microsoft for storing individual chart data within early versions of the Excel spreadsheet application. It was primarily used to isolate graphical representations of data from the parent worksheet before the adoption of integrated workbook formats like XLS and XLSX. While generally considered safe due to its lack of modern macro capabilities, this format is now obsolete and requires legacy software or specialized converters for modern accessibility.
Validation Code
How to validate .xlc files in Python
Python
def is_xlc(file_path: str) -> bool:
"""
Check if file is a valid XLC by magic bytes.
Signature offset: 2080 bytes
"""
signature = bytes([0x4D, 0x69, 0x63, 0x72, 0x6F, 0x73, 0x6F, 0x66, 0x74, 0x20, 0x45, 0x78, 0x63, 0x65, 0x6C, 0x20, 0x35, 0x2E, 0x30, 0x20, 0x57, 0x6F, 0x72, 0x6B, 0x73, 0x68, 0x65, 0x65, 0x74])
with open(file_path, "rb") as f:
f.seek(2080)
return f.read(29) == signatureHow to validate .xlc files in Node.js
Node.js
function isXLC(buffer: Buffer): boolean {
// Signature offset: 2080 bytes
const signature = Buffer.from([0x4D, 0x69, 0x63, 0x72, 0x6F, 0x73, 0x6F, 0x66, 0x74, 0x20, 0x45, 0x78, 0x63, 0x65, 0x6C, 0x20, 0x35, 0x2E, 0x30, 0x20, 0x57, 0x6F, 0x72, 0x6B, 0x73, 0x68, 0x65, 0x65, 0x74]);
if (buffer.length < 2109) return false;
return buffer.subarray(2080, 2109).equals(signature);
}
Go
func IsXLC(data []byte) bool {
// Signature offset: 2080 bytes
signature := []byte{0x4D, 0x69, 0x63, 0x72, 0x6F, 0x73, 0x6F, 0x66, 0x74, 0x20, 0x45, 0x78, 0x63, 0x65, 0x6C, 0x20, 0x35, 0x2E, 0x30, 0x20, 0x57, 0x6F, 0x72, 0x6B, 0x73, 0x68, 0x65, 0x65, 0x74}
if len(data) < 2109 {
return false
}
return bytes.Equal(data[2080:2109], signature)
}API Endpoint
GET
/api/v1/xlc
curl https://filesignature.org/api/v1/xlc