Disable MDNS in Chrome via Chrome policies on the commandline

disable-mdns-chrome.sh

#!/bin/bash
#
# Disable mDNS for Chrome, Chromium and Brave
# Used on Debian 13
#
# Confirm it works:
#   $ lsof -n -i -P | grep -F '224.'
#
# You can/should also just disable multicast on your interfaces if you don't need it
#   $ sudo ifconfig $iface -multicast
#
# @mzpqnxow
# Updated 2026
#
set -euo pipefail

config_blob='{ "EnableMediaRouter": false }'

bases=(
  /etc/opt/chrome
  /etc/brave
  /etc/chromium
)

for base in "${bases[@]}"; do
  file="$base/policies/managed/disable_mdns.json"

  if [[ -f $file ]]; then
    echo "Skipping $file (already exists) with the following content:"
    echo "=== $file ==="
    echo
    cat "$file"
    echo
    echo
    continue
  fi

  echo "Setting $file"
  printf '%s\n' "$config_blob" |
    sudo install -Dm644 /dev/stdin "$file"
done

BTW- there are probably extensions that can disable the mDNS- but a pure configuration change is so much better than adding more code to your system- even if it is (mostly) sandboxed