1Password 4 Cloud Keychain encrypted attachment (.attachment)

.attachment file signature | application/octet-stream

1Password 4 Cloud Keychain encrypted attachment

Safe

Magic Bytes

Offset 0


              4F 50 43 4C 44 41 54

Sources: Gary Kessler

Extension

.attachment

MIME Type

application/octet-stream

Byte Offset

Risk Level

Safe

Validation Code

How to validate .attachment files in Python

Python

def is_attachment(file_path: str) -> bool:
    """Check if file is a valid ATTACHMENT by magic bytes."""
    signature = bytes([0x4F, 0x50, 0x43, 0x4C, 0x44, 0x41, 0x54])
    with open(file_path, "rb") as f:
        return f.read(7) == signature

How to validate .attachment files in Node.js

Node.js

function isATTACHMENT(buffer: Buffer): boolean {
  const signature = Buffer.from([0x4F, 0x50, 0x43, 0x4C, 0x44, 0x41, 0x54]);
  return buffer.subarray(0, 7).equals(signature);
}

How to validate .attachment files in Go

func IsATTACHMENT(data []byte) bool {
    signature := []byte{0x4F, 0x50, 0x43, 0x4C, 0x44, 0x41, 0x54}
    if len(data) < 7 {
        return false
    }
    return bytes.Equal(data[:7], signature)
}

API Endpoint

GET /api/v1/attachment


              curl https://filesignature.org/api/v1/attachment

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .attachment file?

A .attachment file is a 1Password 4 Cloud Keychain encrypted attachment file. 1Password 4 Cloud Keychain encrypted attachment

What are the magic bytes for .attachment files?

The magic bytes for 1Password 4 Cloud Keychain encrypted attachment files are 4F 50 43 4C 44 41 54 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .attachment file?

To validate a .attachment file, read the first bytes of the file and compare them against the known magic bytes (4F 50 43 4C 44 41 54) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .attachment files?

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

Is it safe to open .attachment files?

1Password 4 Cloud Keychain encrypted attachment (.attachment) 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.