MS audio compression manager driver magic bytes (.acm)
.acm file signature: 4D 5A | application/octet-stream
Audio Compression Manager (ACM) is a legacy Microsoft driver format maintained as part of the Windows audio subsystem. It is used to provide audio codec support for encoding and decoding compressed sound data in older multimedia applications and system components. As an older Windows format, it is generally safe, though compatibility may be limited on modern systems and files from untrusted sources should still be handled carefully.
Magic Bytes
Offset 0
4D 5A
Sources: Gary Kessler
Validation Code
How to validate .acm files in Python
def is_acm(file_path: str) -> bool:
"""Check if file is a valid ACM by magic bytes."""
signature = bytes([0x4D, 0x5A])
with open(file_path, "rb") as f:
return f.read(2) == signatureHow to validate .acm files in Node.js
function isACM(buffer: Buffer): boolean {
const signature = Buffer.from([0x4D, 0x5A]);
return buffer.subarray(0, 2).equals(signature);
}How to validate .acm files in Go
func IsACM(data []byte) bool {
signature := []byte{0x4D, 0x5A}
if len(data) < 2 {
return false
}
return bytes.Equal(data[:2], signature)
}API Endpoint
/api/v1/acm
curl https://filesignature.org/api/v1/acm
See the full API documentation for all endpoints and parameters.
Frequently Asked Questions
What is a .acm file?
A .acm file is an MS audio compression manager driver file. Audio Compression Manager (ACM) is a legacy Microsoft driver format maintained as part of the Windows audio subsystem. It is used to provide audio codec support for encoding and decoding compressed sound data in older multimedia applications and system components. As an older Windows format, it is generally safe, though compatibility may be limited on modern systems and files from untrusted sources should still be handled carefully.
What are the magic bytes for .acm files?
The magic bytes for MS audio compression manager driver (.acm) files are 4D 5A at byte offset 0. These bytes identify the file format more reliably than the extension alone.
How do I validate a .acm file?
To validate a .acm file, read the first bytes of the file and compare them against the known magic bytes (4D 5A) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.
What is the MIME type for .acm files?
There is no officially registered MIME type for .acm files. Systems typically use application/octet-stream as a generic fallback when handling this format.
Is it safe to open .acm files?
MS audio compression manager driver (.acm) 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.