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OneNote Package file magic bytes (.onepkg)

.onepkg file signature: 4D 53 43 46 | application/onenote; format=package

OneNote Package (ONEPKG) is a Microsoft file format used to package Microsoft OneNote notebook content for distribution and archiving. It is used for sharing notebooks, transferring notes between devices, and storing collections of pages, sections, and attachments in a single file. The format is generally safe, but like other document containers it may include embedded files or links, so opening packages from untrusted sources should be done with caution.

Safe

Magic Bytes

Offset 0
4D 53 43 46

Sources: Gary Kessler

Extension

.onepkg

MIME Type

application/onenote; format=package

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .onepkg files in Python

Python 
def is_onepkg(file_path: str) -> bool:
    """Check if file is a valid ONEPKG by magic bytes."""
    signature = bytes([0x4D, 0x53, 0x43, 0x46])
    with open(file_path, "rb") as f:
        return f.read(4) == signature

How to validate .onepkg files in Node.js

Node.js 
function isONEPKG(buffer: Buffer): boolean {
  const signature = Buffer.from([0x4D, 0x53, 0x43, 0x46]);
  return buffer.subarray(0, 4).equals(signature);
}

How to validate .onepkg files in Go

Go 
func IsONEPKG(data []byte) bool {
    signature := []byte{0x4D, 0x53, 0x43, 0x46}
    if len(data) < 4 {
        return false
    }
    return bytes.Equal(data[:4], signature)
}

API Endpoint

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

See the full API documentation for all endpoints and parameters.

Related Formats

.cab .snp

Frequently Asked Questions

What is a .onepkg file?

A .onepkg file is an OneNote Package file. OneNote Package (ONEPKG) is a Microsoft file format used to package Microsoft OneNote notebook content for distribution and archiving. It is used for sharing notebooks, transferring notes between devices, and storing collections of pages, sections, and attachments in a single file. The format is generally safe, but like other document containers it may include embedded files or links, so opening packages from untrusted sources should be done with caution.

What are the magic bytes for .onepkg files?

The magic bytes for OneNote Package file (.onepkg) files are 4D 53 43 46 at byte offset 0. These bytes identify the file format more reliably than the extension alone.

How do I validate a .onepkg file?

To validate a .onepkg file, read the first bytes of the file and compare them against the known magic bytes (4D 53 43 46) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .onepkg files?

The primary MIME type for .onepkg files is application/onenote; format=package.

Is it safe to open .onepkg files?

OneNote Package file (.onepkg) 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.