Library cache file (.ax)

.ax file signature | application/octet-stream

DOS MZ executableand its descendants (includingNEandPE)

Safe

Magic Bytes

Offset 0


              4D 5A

Sources: Wikipedia, Gary Kessler

All Known Signatures

2 signature variants are documented for .ax files across multiple sources.

Hex Signature	Offset	Sources
4D 5A	0	Wikipedia, Gary Kessler
4D 5A 90 00 03 00 00 00	0	Gary Kessler

Extension

.ax

MIME Type

application/octet-stream

Byte Offset

Risk Level

Safe

Validation Code

How to validate .ax files in Python

Python

def is_ax(file_path: str) -> bool:
    """Check if file is a valid AX by magic bytes."""
    signature = bytes([0x4D, 0x5A])
    with open(file_path, "rb") as f:
        return f.read(2) == signature

How to validate .ax files in Node.js

Node.js

function isAX(buffer: Buffer): boolean {
  const signature = Buffer.from([0x4D, 0x5A]);
  return buffer.subarray(0, 2).equals(signature);
}

How to validate .ax files in Go

func IsAX(data []byte) bool {
    signature := []byte{0x4D, 0x5A}
    if len(data) < 2 {
        return false
    }
    return bytes.Equal(data[:2], signature)
}

API Endpoint

GET /api/v1/ax


              curl https://filesignature.org/api/v1/ax

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .ax file?

A .ax file is a Library cache file file. DOS MZ executableand its descendants (includingNEandPE)

What are the magic bytes for .ax files?

The magic bytes for Library cache file files are 4D 5A at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .ax file?

To validate a .ax 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 .ax files?

There is no officially registered MIME type for .ax files. Systems typically use application/octet-stream as a generic fallback when handling this format.

Is it safe to open .ax files?

Library cache file (.ax) 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.