Microsoft cabinet file (.cab)
.cab file signature | application/vnd.ms-cab-compressed
Microsoft Cabinet (CAB) is an archive file format developed and maintained by Microsoft for compressing and packaging files. It is used to distribute software components, Windows updates, device drivers, and installation resources, and it is supported by Windows system tools and several archival utilities. CAB files are generally safe, but like other archives they can conceal malicious content; the format is also associated with older Windows installation and deployment workflows.
Magic Bytes
Offset 0
4D 53 43 46
Sources: Apache Tika, Wikipedia, Gary Kessler, Neil Harvey FileSignatures
All Known Signatures
3 signature variants are documented for .cab files across multiple sources.
| Hex Signature | Offset | Sources |
|---|---|---|
| 4D 53 43 46 | 0 | Apache Tika, Wikipedia, Gary Kessler, Neil Harvey FileSignatures |
| 49 53 63 28 | 0 | Wikipedia, Gary Kessler |
| 4D 53 43 46 00 00 00 00 | 0 | Apache Tika |
Extension
.cab
MIME Type
application/vnd.ms-cab-compressed
Byte Offset
0
Risk Level
Safe
Validation Code
How to validate .cab files in Python
def is_cab(file_path: str) -> bool:
"""Check if file is a valid CAB by magic bytes."""
signature = bytes([0x4D, 0x53, 0x43, 0x46])
with open(file_path, "rb") as f:
return f.read(4) == signatureHow to validate .cab files in Node.js
function isCAB(buffer: Buffer): boolean {
const signature = Buffer.from([0x4D, 0x53, 0x43, 0x46]);
return buffer.subarray(0, 4).equals(signature);
}How to validate .cab files in Go
func IsCAB(data []byte) bool {
signature := []byte{0x4D, 0x53, 0x43, 0x46}
if len(data) < 4 {
return false
}
return bytes.Equal(data[:4], signature)
}API Endpoint
/api/v1/cab
curl https://filesignature.org/api/v1/cab
See the full API documentation for all endpoints and parameters.
Related Formats
Frequently Asked Questions
What is a .cab file?
A .cab file is a Microsoft cabinet file file. Microsoft Cabinet (CAB) is an archive file format developed and maintained by Microsoft for compressing and packaging files. It is used to distribute software components, Windows updates, device drivers, and installation resources, and it is supported by Windows system tools and several archival utilities. CAB files are generally safe, but like other archives they can conceal malicious content; the format is also associated with older Windows installation and deployment workflows.
What are the magic bytes for .cab files?
The magic bytes for Microsoft cabinet file files are 4D 53 43 46 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.
How do I validate a .cab file?
To validate a .cab file, read the first bytes of the file and compare them against the known magic bytes (4D 53 43 46) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.
What is the MIME type for .cab files?
The primary MIME type for .cab files is application/vnd.ms-cab-compressed.
Is it safe to open .cab files?
Microsoft cabinet file (.cab) 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.