OpenType font file
application/x-font-otf
Magic Bytes
Offset: 0
4F 54 54 4F 00
OpenType font file (OTF) is a cross-platform font format developed by Microsoft and Adobe as an evolutionary successor to the TrueType standard. It is widely implemented across operating systems and design software to provide advanced typographic features, including ligatures, small caps, and extensive character sets for global languages. While functionally safe, the format relies on complex parsing engines within the operating system kernel, which necessitates keeping software updated to prevent potential font-processing exploits.
Validation Code
How to validate .otf files in Python
Python
def is_otf(file_path: str) -> bool:
"""Check if file is a valid OTF by magic bytes."""
signature = bytes([0x4F, 0x54, 0x54, 0x4F, 0x00])
with open(file_path, "rb") as f:
return f.read(5) == signatureHow to validate .otf files in Node.js
Node.js
function isOTF(buffer: Buffer): boolean {
const signature = Buffer.from([0x4F, 0x54, 0x54, 0x4F, 0x00]);
return buffer.subarray(0, 5).equals(signature);
}
Go
func IsOTF(data []byte) bool {
signature := []byte{0x4F, 0x54, 0x54, 0x4F, 0x00}
if len(data) < 5 {
return false
}
return bytes.Equal(data[:5], signature)
}API Endpoint
GET
/api/v1/otf
curl https://filesignature.org/api/v1/otf