AOL HTML mail file
application/octet-stream
Magic Bytes
Offset: 0
3C 3F
The AOL HTML mail file (DCI) is a proprietary data structure developed by America Online for the storage of electronic mail messages. This legacy format was utilized by early versions of the AOL client software to organize and display local HTML-formatted email content on a user's computer. As a text-based format containing standard markup, it is generally considered safe, although it is now obsolete and primarily found in archives of older digital communications.
Validation Code
How to validate .dci files in Python
Python
def is_dci(file_path: str) -> bool:
"""Check if file is a valid DCI by magic bytes."""
signature = bytes([0x3C, 0x3F])
with open(file_path, "rb") as f:
return f.read(2) == signatureHow to validate .dci files in Node.js
Node.js
function isDCI(buffer: Buffer): boolean {
const signature = Buffer.from([0x3C, 0x3F]);
return buffer.subarray(0, 2).equals(signature);
}
Go
func IsDCI(data []byte) bool {
signature := []byte{0x3C, 0x3F}
if len(data) < 2 {
return false
}
return bytes.Equal(data[:2], signature)
}API Endpoint
GET
/api/v1/dci
curl https://filesignature.org/api/v1/dci