What is a DMZ or exposed host on a router?

What it is

A router normally acts like a front door with a lock. It lets in only the replies to things your devices asked for. A setting called DMZ (also DMZ host, Exposed Host or Default Server) tells the router to send everything that arrives from the internet straight to one chosen device in your home.

That takes away much of the router's protection for that device. It is sometimes switched on by a gamer or a camera installer as a shortcut to make something work.

Why it matters

Our check looks at your home from the outside. If DMZ is on, it can find many open doors at once, because the chosen device is now reachable from the internet. Most homes do not need it.

How to check

1. Sign in to your router.
2. Look for DMZ, Exposed Host or Default Server. It is often under Advanced, NAT, Firewall or Port Forwarding.
3. If it is off or disabled, you are fine. Nothing to do.
4. If it is on, note the number next to it (an address like 192.168.1.20). Our guide Which device is this? shows how to find out what that device is.
5. If you do not know why it is on, switch it to Off and press Save.

If something stops working

If a game or camera stops working after you turn it off, do not turn DMZ back on. Ask someone you trust to open just the one door that app needs, which is safer. Or use the maker's phone app, which usually works without opening anything.