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

Did you check after an hour or two of usage? I'm finding that the mDNS listening comes back after an hour.

Thanks! I can confirm this seems to have realllly slows down Chrome's spam. (For anyone else on macOS, you need to make a .mobileconfig profile to flip EnableMediaRouter to false.)

actually, now I'm seeing the same thing @davehayes is. Eventually Chrome goes back to mDNS listening and resolving every ._googcast._tcp.local. service every time one is announced... If you have a lot of Chromecasts and GHome on your network then that means your Chrome will be constantly busy. (GDevices are spammy and their mDNS broadcast traffic rates grows O(n^2) where n is the number of GDevices)

The #enable-webrtc-hide-local-ips-with-mdns flag no longer showed up for me on chrome 87.0.4280.88. Enabling the flag #temporary-unexpire-flags-m85 showed this flag again but after finally setting #enable-webrtc-hide-local-ips-with-mdns to Disabled, the mDNS entries reappeared again after a while as others mentioned.

You can try setting the immutable flag on the configuration file after you modify it. You’ll need elevated privileges to do so, though

The simplest way to do a basic test would be to shut down all chrome instances, make the change, then sudo chattr +i . Until you chattr -i the file, it won’t be mutable by any users (not even root)

The file has to be on an ext-based file system because it uses the extfs extended attributes

You could also try just chowning it to root, but it’s possible it could be deleted and recreated as a normal user since the directory will be owned by a normal user

good luck, let me know if you figure anything out. I stopped using Chrome entirely a while ago so haven’t looked at it all on probably over a year

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