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ONETOC2 (.onetoc2)

.onetoc2 file signature | application/onenote;format=onetoc2

Safe

Magic Bytes

Offset 0
43 FF 2F A1

Sources: Apache Tika

Extension

.onetoc2

MIME Type

application/onenote;format=onetoc2

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .onetoc2 files in Python

Python 
def is_onetoc2(file_path: str) -> bool:
    """Check if file is a valid ONETOC2 by magic bytes."""
    signature = bytes([0x43, 0xFF, 0x2F, 0xA1])
    with open(file_path, "rb") as f:
        return f.read(4) == signature

How to validate .onetoc2 files in Node.js

Node.js 
function isONETOC2(buffer: Buffer): boolean {
  const signature = Buffer.from([0x43, 0xFF, 0x2F, 0xA1]);
  return buffer.subarray(0, 4).equals(signature);
}

How to validate .onetoc2 files in Go

Go 
func IsONETOC2(data []byte) bool {
    signature := []byte{0x43, 0xFF, 0x2F, 0xA1}
    if len(data) < 4 {
        return false
    }
    return bytes.Equal(data[:4], signature)
}

API Endpoint

GET /api/v1/onetoc2
curl https://filesignature.org/api/v1/onetoc2

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .onetoc2 file?

A .onetoc2 file is a ONETOC2 file.

What are the magic bytes for .onetoc2 files?

The magic bytes for ONETOC2 files are 43 FF 2F A1 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .onetoc2 file?

To validate a .onetoc2 file, read the first bytes of the file and compare them against the known magic bytes (43 FF 2F A1) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .onetoc2 files?

The primary MIME type for .onetoc2 files is application/onenote;format=onetoc2.

Is it safe to open .onetoc2 files?

ONETOC2 (.onetoc2) 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.