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CWK (.cwk)

.cwk file signature | application/octet-stream

Claris Works word processing doc

Safe

Magic Bytes

Offset 0
02 00 5A 57 52 54 00 00 00 00 00 00 00 00 00 00

Sources: Wikipedia

All Known Signatures

3 signature variants are documented for .cwk files across multiple sources.

Hex Signature Offset Sources
02 00 5A 57 52 54 00 00 00 00 00 00 00 00 00 00 0 Wikipedia
05 07 00 00 42 4F 42 4F 05 07 00 00 00 00 00 00 00 00 00 00 00 01 0 Wikipedia
06 07 E1 00 42 4F 42 4F 06 07 E1 00 00 00 00 00 00 00 00 00 00 01 0 Wikipedia

Extension

.cwk

MIME Type

application/octet-stream

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .cwk files in Python

Python 
def is_cwk(file_path: str) -> bool:
    """Check if file is a valid CWK by magic bytes."""
    signature = bytes([0x02, 0x00, 0x5A, 0x57, 0x52, 0x54, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    with open(file_path, "rb") as f:
        return f.read(16) == signature

How to validate .cwk files in Node.js

Node.js 
function isCWK(buffer: Buffer): boolean {
  const signature = Buffer.from([0x02, 0x00, 0x5A, 0x57, 0x52, 0x54, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]);
  return buffer.subarray(0, 16).equals(signature);
}

How to validate .cwk files in Go

Go 
func IsCWK(data []byte) bool {
    signature := []byte{0x02, 0x00, 0x5A, 0x57, 0x52, 0x54, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}
    if len(data) < 16 {
        return false
    }
    return bytes.Equal(data[:16], signature)
}

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .cwk file?

A .cwk file is a CWK file. Claris Works word processing doc

What are the magic bytes for .cwk files?

The magic bytes for CWK files are 02 00 5A 57 52 54 00 00 00 00 00 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 .cwk file?

To validate a .cwk file, read the first bytes of the file and compare them against the known magic bytes (02 00 5A 57 52 54 00 00 00 00 00 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 .cwk files?

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

Is it safe to open .cwk files?

CWK (.cwk) 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.