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Lotus 1-2-3 spreadsheet (.wk5)

.wk5 file signature | application/octet-stream

Lotus 1-2-3 spreadsheet (v4, v5) file

Safe

Magic Bytes

Offset 0
00 00 1A 00 02 10 04 00 00 00 00 00

Sources: Wikipedia, Gary Kessler

Extension

.wk5

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .wk5 files in Python

Python 
def is_wk5(file_path: str) -> bool:
    """Check if file is a valid WK5 by magic bytes."""
    signature = bytes([0x00, 0x00, 0x1A, 0x00, 0x02, 0x10, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00])
    with open(file_path, "rb") as f:
        return f.read(12) == signature

How to validate .wk5 files in Node.js

Node.js 
function isWK5(buffer: Buffer): boolean {
  const signature = Buffer.from([0x00, 0x00, 0x1A, 0x00, 0x02, 0x10, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00]);
  return buffer.subarray(0, 12).equals(signature);
}

How to validate .wk5 files in Go

Go 
func IsWK5(data []byte) bool {
    signature := []byte{0x00, 0x00, 0x1A, 0x00, 0x02, 0x10, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00}
    if len(data) < 12 {
        return false
    }
    return bytes.Equal(data[:12], signature)
}

API Endpoint

GET /api/v1/wk5
curl https://filesignature.org/api/v1/wk5

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .wk5 file?

A .wk5 file is a Lotus 1-2-3 spreadsheet file. Lotus 1-2-3 spreadsheet (v4, v5) file

What are the magic bytes for .wk5 files?

The magic bytes for Lotus 1-2-3 spreadsheet files are 00 00 1A 00 02 10 04 00 00 00 00 00 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .wk5 file?

To validate a .wk5 file, read the first bytes of the file and compare them against the known magic bytes (00 00 1A 00 02 10 04 00 00 00 00 00) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .wk5 files?

There is no officially registered MIME type for .wk5 files. Systems typically use application/octet-stream as a generic fallback when handling this format.

Is it safe to open .wk5 files?

Lotus 1-2-3 spreadsheet (.wk5) 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.