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XLL (.xll)

.xll file signature | application/vnd.ms-excel

Safe

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

Sources: Apache Tika

All Known Signatures

5 signature variants are documented for .xll files across multiple sources.

Hex Signature Offset Sources
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 2080 Apache Tika
46 6F 67 6C 69 6F 20 64 69 20 6C 61 76 6F 72 6F 20 4D 69 63 72 6F 73 6F 66 74 20 45 78 63 65 2080 Apache Tika
42 69 66 66 35 2114 Apache Tika
42 69 66 66 35 2121 Apache Tika
D0 CF 11 E0 A1 B1 1A E1 0 Apache Tika

Extension

.xll

MIME Type

application/vnd.ms-excel

Byte Offset

2080

Risk Level

Safe

Validation Code

How to validate .xll files in Python

Python 
def is_xll(file_path: str) -> bool:
    """Check if file is a valid XLL by magic 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:
        return f.read(29) == signature

How to validate .xll files in Node.js

Node.js 
function isXLL(buffer: Buffer): boolean {
  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]);
  return buffer.subarray(0, 29).equals(signature);
}

How to validate .xll files in Go

Go 
func IsXLL(data []byte) bool {
    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) < 29 {
        return false
    }
    return bytes.Equal(data[:29], signature)
}

API Endpoint

GET /api/v1/xll
curl https://filesignature.org/api/v1/xll

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .xll file?

A .xll file is a XLL file.

What are the magic bytes for .xll files?

The magic bytes for XLL files are 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 at byte offset 2080. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .xll file?

To validate a .xll file, read the first bytes of the file and compare them against the known magic bytes (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) at offset 2080. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .xll files?

The primary MIME type for .xll files is application/vnd.ms-excel.

Is it safe to open .xll files?

XLL (.xll) files are generally safe to open. They are classified as low risk because they primarily contain data rather than executable code. However, always ensure files come from a trusted source.