Microsoft/MSN MARC archive (.mar)
.mar file signature | application/octet-stream
Microsoft/MSN MARC archive is a file format developed by Microsoft for packaging data used by MSN-related components and maintained as part of legacy Microsoft software ecosystems. It was primarily used to store resources, metadata, or update content for applications and installation packages associated with older Microsoft services. The format is largely historical and may be encountered in archived software; files are generally safe to inspect but should still be opened cautiously when obtained from untrusted sources.
Magic Bytes
Offset 0
4D 41 52 31 00
Sources: Gary Kessler
All Known Signatures
3 signature variants are documented for .mar files across multiple sources.
| Hex Signature | Offset | Sources |
|---|---|---|
| 4D 41 52 31 00 | 0 | Gary Kessler |
| 4D 41 52 43 | 0 | Gary Kessler |
| 4D 41 72 30 00 | 0 | Gary Kessler |
Extension
.mar
MIME Type
application/octet-stream
Byte Offset
0
Risk Level
Safe
Validation Code
How to validate .mar files in Python
def is_mar(file_path: str) -> bool:
"""Check if file is a valid MAR by magic bytes."""
signature = bytes([0x4D, 0x41, 0x52, 0x31, 0x00])
with open(file_path, "rb") as f:
return f.read(5) == signatureHow to validate .mar files in Node.js
function isMAR(buffer: Buffer): boolean {
const signature = Buffer.from([0x4D, 0x41, 0x52, 0x31, 0x00]);
return buffer.subarray(0, 5).equals(signature);
}How to validate .mar files in Go
func IsMAR(data []byte) bool {
signature := []byte{0x4D, 0x41, 0x52, 0x31, 0x00}
if len(data) < 5 {
return false
}
return bytes.Equal(data[:5], signature)
}API Endpoint
/api/v1/mar
curl https://filesignature.org/api/v1/mar
See the full API documentation for all endpoints and parameters.
Frequently Asked Questions
What is a .mar file?
A .mar file is a Microsoft/MSN MARC archive file. Microsoft/MSN MARC archive is a file format developed by Microsoft for packaging data used by MSN-related components and maintained as part of legacy Microsoft software ecosystems. It was primarily used to store resources, metadata, or update content for applications and installation packages associated with older Microsoft services. The format is largely historical and may be encountered in archived software; files are generally safe to inspect but should still be opened cautiously when obtained from untrusted sources.
What are the magic bytes for .mar files?
The magic bytes for Microsoft/MSN MARC archive files are 4D 41 52 31 00 at byte offset 0. These bytes uniquely identify the file format regardless of the file extension.
How do I validate a .mar file?
To validate a .mar file, read the first bytes of the file and compare them against the known magic bytes (4D 41 52 31 00) at offset 0. This is more reliable than checking the file extension alone, as extensions can be renamed.
What is the MIME type for .mar files?
There is no officially registered MIME type for .mar files. Systems typically use application/octet-stream as a generic fallback when handling this format.
Is it safe to open .mar files?
Microsoft/MSN MARC archive (.mar) 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.