1Password 4 Cloud Keychain encrypted attachment magic bytes (.attachment)
.attachment file signature: 4F 50 43 4C 44 41 54 | application/octet-stream
1Password 4 Cloud Keychain encrypted attachment is a proprietary file format used by 1Password, developed and maintained by AgileBits, for storing encrypted attachment data. It is used within 1Password vaults and synced keychain-based environments to preserve files associated with saved items such as documents, images, and records. The format is considered safe in normal use, but its contents remain encrypted and are intended to be accessed only through compatible 1Password software.
Magic Bytes
Offset 0
4F 50 43 4C 44 41 54
Sources: Gary Kessler
Validation Code
How to validate .attachment files in 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) == signatureHow to validate .attachment files in 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
/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 is a proprietary file format used by 1Password, developed and maintained by AgileBits, for storing encrypted attachment data. It is used within 1Password vaults and synced keychain-based environments to preserve files associated with saved items such as documents, images, and records. The format is considered safe in normal use, but its contents remain encrypted and are intended to be accessed only through compatible 1Password software.
What are the magic bytes for .attachment files?
The magic bytes for 1Password 4 Cloud Keychain encrypted attachment (.attachment) files are 4F 50 43 4C 44 41 54 at byte offset 0. These bytes identify the file format more reliably than the extension alone.
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.