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Lotus 1-2-3 spreadsheet (.wk4)

.wk4 file signature | application/vnd.lotus-1-2-3;version=4

Lotus 1-2-3 spreadsheet (WK4) is a legacy spreadsheet file format created by Lotus Development Corporation for the Lotus 1-2-3 application, later supported by IBM after its acquisition of Lotus. It was used for business spreadsheets, calculations, and tabular data exchange in desktop productivity suites such as Lotus 1-2-3 and compatible office software. The format is obsolete and, like other legacy spreadsheets, should be opened with trusted software when handling older files.

Safe

Magic Bytes

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

Sources: Wikipedia, Gary Kessler

All Known Signatures

2 signature variants are documented for .wk4 files across multiple sources.

Hex Signature Offset Sources
00 00 1A 00 02 10 04 00 00 00 00 00 0 Wikipedia, Gary Kessler
00 00 1A 00 02 10 04 00 0 Apache Tika

Extension

.wk4

MIME Type

application/vnd.lotus-1-2-3;version=4

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .wk4 files in Python

Python 
def is_wk4(file_path: str) -> bool:
    """Check if file is a valid WK4 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 .wk4 files in Node.js

Node.js 
function isWK4(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 .wk4 files in Go

Go 
func IsWK4(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/wk4
curl https://filesignature.org/api/v1/wk4

See the full API documentation for all endpoints and parameters.

Related Formats

.wk3 .wk5 .123 .wk1

Frequently Asked Questions

What is a .wk4 file?

A .wk4 file is a Lotus 1-2-3 spreadsheet file. Lotus 1-2-3 spreadsheet (WK4) is a legacy spreadsheet file format created by Lotus Development Corporation for the Lotus 1-2-3 application, later supported by IBM after its acquisition of Lotus. It was used for business spreadsheets, calculations, and tabular data exchange in desktop productivity suites such as Lotus 1-2-3 and compatible office software. The format is obsolete and, like other legacy spreadsheets, should be opened with trusted software when handling older files.

What are the magic bytes for .wk4 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 .wk4 file?

To validate a .wk4 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 .wk4 files?

The primary MIME type for .wk4 files is application/vnd.lotus-1-2-3;version=4.

Is it safe to open .wk4 files?

Lotus 1-2-3 spreadsheet (.wk4) 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.