DOCX Word Open XML Document

SIGNATURE = bytes.fromhex("504b0304")
OFFSET = 0

def is_docx(path: str) -> bool:
    with open(path, "rb") as f:
        f.seek(OFFSET)
        head = f.read(len(SIGNATURE))
    return head == SIGNATURE

const SIGNATURE = [0x50, 0x4b, 0x03, 0x04];
const OFFSET = 0;

// bytes: a Uint8Array / Buffer holding the start of the file
export function isDocx(bytes) {
  return SIGNATURE.every((byte, i) => bytes[OFFSET + i] === byte);
}

package fileid

import "bytes"

var isdocxSignature = []byte{0x50, 0x4b, 0x03, 0x04}

const isdocxOffset = 0

func IsDocx(b []byte) bool {
	end := isdocxOffset + len(isdocxSignature)
	if len(b) < end {
		return false
	}
	return bytes.Equal(b[isdocxOffset:end], isdocxSignature)
}

const SIGNATURE: &[u8] = &[0x50, 0x4b, 0x03, 0x04];
const OFFSET: usize = 0;

fn is_docx(bytes: &[u8]) -> bool {
    bytes.get(OFFSET..OFFSET + SIGNATURE.len()) == Some(SIGNATURE)
}

<?php
$signature = "\x50\x4b\x03\x04";
$offset = 0;

function is_docx(string $bytes): bool {
    global $signature, $offset;
    return substr($bytes, $offset, strlen($signature)) === $signature;
}