Compressed ISO
application/octet-stream
Magic Bytes
Offset: 0
43 4D 4D 4D 15 00 00 00
Compressed ISO (CSO) is a lossless disk image compression format originally developed by the PlayStation Portable homebrew community. It is primarily utilized within console emulation and handheld gaming environments to store optical disc backups on storage devices with limited capacity. Although newer formats now offer higher compression efficiency, CSO remains a legacy standard for archiving game data and presents minimal security risks to users due to its read-only nature.
Validation Code
How to validate .cso files in Python
Python
def is_cso(file_path: str) -> bool:
"""Check if file is a valid CSO by magic bytes."""
signature = bytes([0x43, 0x4D, 0x4D, 0x4D, 0x15, 0x00, 0x00, 0x00])
with open(file_path, "rb") as f:
return f.read(8) == signatureHow to validate .cso files in Node.js
Node.js
function isCSO(buffer: Buffer): boolean {
const signature = Buffer.from([0x43, 0x4D, 0x4D, 0x4D, 0x15, 0x00, 0x00, 0x00]);
return buffer.subarray(0, 8).equals(signature);
}
Go
func IsCSO(data []byte) bool {
signature := []byte{0x43, 0x4D, 0x4D, 0x4D, 0x15, 0x00, 0x00, 0x00}
if len(data) < 8 {
return false
}
return bytes.Equal(data[:8], signature)
}API Endpoint
GET
/api/v1/cso
curl https://filesignature.org/api/v1/cso