NeXT/Sun Microsystems µ-Law audio file
audio/basic
Magic Bytes
Offset: 0
2E 73 6E 64
The AU file format is a digital audio container originally developed by Sun Microsystems and NeXT for use on Unix-based operating systems. It primarily stores spoken audio and sound effects using logarithmic encoding techniques such as µ-law or A-law. Although now considered a legacy format largely superseded by modern standards like WAV or MP3, it remains safe for general playback and is still supported by most multimedia software applications and diverse Unix environments.
Validation Code
How to validate .au files in Python
Python
def is_au(file_path: str) -> bool:
"""Check if file is a valid AU by magic bytes."""
signature = bytes([0x2E, 0x73, 0x6E, 0x64])
with open(file_path, "rb") as f:
return f.read(4) == signatureHow to validate .au files in Node.js
Node.js
function isAU(buffer: Buffer): boolean {
const signature = Buffer.from([0x2E, 0x73, 0x6E, 0x64]);
return buffer.subarray(0, 4).equals(signature);
}
Go
func IsAU(data []byte) bool {
signature := []byte{0x2E, 0x73, 0x6E, 0x64}
if len(data) < 4 {
return false
}
return bytes.Equal(data[:4], signature)
}API Endpoint
GET
/api/v1/au
curl https://filesignature.org/api/v1/au