Windows Icon (Legacy MIME)

import magic
# Libmagic natively detects the ICO magic bytes
print(magic.from_file('favicon.ico', mime=True)) # Outputs 'image/vnd.microsoft.icon' or 'image/x-icon'

const fs = require('fs');
// Manually detecting the ICO magic bytes (00 00 01 00)
const buffer = Buffer.alloc(4);
const fd = fs.openSync('favicon.ico', 'r');
fs.readSync(fd, buffer, 0, 4, 0);
fs.closeSync(fd);
const isICO = buffer[0] === 0x00 && buffer[1] === 0x00 && buffer[2] === 0x01 && buffer[3] === 0x00;
console.log('Is Windows ICO:', isICO);

import (
    "bytes"
    "net/http"
)
// Native Go HTTP detection reads the ICO magic bytes natively
// mime := http.DetectContentType(buf) // Returns "image/x-icon"

$mime = mime_content_type('favicon.ico');
echo $mime; // Standard setups will often resolve this to 'image/vnd.microsoft.icon' or 'image/x-icon'