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K-9 Mailsettings file (.k9s)

.k9s file signature | application/octet-stream

K-9 Mailsettings file (Android e-mail app)

Safe

Magic Bytes

Offset 58
3C 6B 39 73 65 74 74 69 6E 67 73

Sources: Gary Kessler

Extension

.k9s

MIME Type

application/octet-stream

Byte Offset

58

Risk Level

Safe

Validation Code

How to validate .k9s files in Python

Python 
def is_k9s(file_path: str) -> bool:
    """Check if file is a valid K9S by magic bytes."""
    signature = bytes([0x3C, 0x6B, 0x39, 0x73, 0x65, 0x74, 0x74, 0x69, 0x6E, 0x67, 0x73])
    with open(file_path, "rb") as f:
        return f.read(11) == signature

How to validate .k9s files in Node.js

Node.js 
function isK9S(buffer: Buffer): boolean {
  const signature = Buffer.from([0x3C, 0x6B, 0x39, 0x73, 0x65, 0x74, 0x74, 0x69, 0x6E, 0x67, 0x73]);
  return buffer.subarray(0, 11).equals(signature);
}

How to validate .k9s files in Go

Go 
func IsK9S(data []byte) bool {
    signature := []byte{0x3C, 0x6B, 0x39, 0x73, 0x65, 0x74, 0x74, 0x69, 0x6E, 0x67, 0x73}
    if len(data) < 11 {
        return false
    }
    return bytes.Equal(data[:11], signature)
}

API Endpoint

GET /api/v1/k9s
curl https://filesignature.org/api/v1/k9s

See the full API documentation for all endpoints and parameters.

Frequently Asked Questions

What is a .k9s file?

A .k9s file is a K-9 Mailsettings file file. K-9 Mailsettings file (Android e-mail app)

What are the magic bytes for .k9s files?

The magic bytes for K-9 Mailsettings file files are 3C 6B 39 73 65 74 74 69 6E 67 73 at byte offset 58. These bytes uniquely identify the file format regardless of the file extension.

How do I validate a .k9s file?

To validate a .k9s file, read the first bytes of the file and compare them against the known magic bytes (3C 6B 39 73 65 74 74 69 6E 67 73) at offset 58. This is more reliable than checking the file extension alone, as extensions can be renamed.

What is the MIME type for .k9s files?

There is no officially registered MIME type for .k9s files. Systems typically use application/octet-stream as a generic fallback when handling this format.

Is it safe to open .k9s files?

K-9 Mailsettings file (.k9s) 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.