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ONETOC (.onetoc)

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

ONETOC is a Microsoft OneNote table of contents file format used by Microsoft OneNote to organize notebook structure and section metadata. It is primarily used by OneNote desktop applications to store navigation information for notebooks and related sections. The format is generally safe and lightweight, though it is tied to legacy and current OneNote implementations and is not intended for direct editing by users.

Safe

Magic Bytes

Offset 0
43 FF 2F A1

Sources: Apache Tika

Extension

.onetoc

MIME Type

application/onenote;format=onetoc2

Byte Offset

0

Risk Level

Safe

Validation Code

How to validate .onetoc files in Python

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

How to validate .onetoc files in Node.js

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

How to validate .onetoc files in Go

Go 
func IsONETOC(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/onetoc
curl https://filesignature.org/api/v1/onetoc

See the full API documentation for all endpoints and parameters.

Related Formats

.onetoc2

Frequently Asked Questions

What is a .onetoc file?

A .onetoc file is identified by the magic bytes 43 FF 2F A1 at byte offset 0. ONETOC is a Microsoft OneNote table of contents file format used by Microsoft OneNote to organize notebook structure and section metadata. It is primarily used by OneNote desktop applications to store navigation information for notebooks and related sections. The format is generally safe and lightweight, though it is tied to legacy and current OneNote implementations and is not intended for direct editing by users.

What are the magic bytes for .onetoc files?

The magic bytes for ONETOC 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 .onetoc file?

To validate a .onetoc 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 .onetoc files?

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

Is it safe to open .onetoc files?

ONETOC (.onetoc) 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.