Library cache file magic bytes (.ax)
.ax file signature: 4D 5A | application/octet-stream
The AX file format is a Windows executable and library container based on the MZ program format, originally created for MS-DOS and maintained through Microsoft’s Windows loader conventions. It is used for application components, shared libraries, and system modules loaded by Windows-based software and related development tools. As a legacy format with broad historical compatibility, AX files should be obtained from trusted sources, since they can contain executable code and may pose the same risks as other Windows binaries.
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 |
Validation Code
How to validate .ax files in 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) == signatureHow to validate .ax files in 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
/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. The AX file format is a Windows executable and library container based on the MZ program format, originally created for MS-DOS and maintained through Microsoft’s Windows loader conventions. It is used for application components, shared libraries, and system modules loaded by Windows-based software and related development tools. As a legacy format with broad historical compatibility, AX files should be obtained from trusted sources, since they can contain executable code and may pose the same risks as other Windows binaries.
What are the magic bytes for .ax files?
The magic bytes for Library cache file (.ax) 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 .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.