How to Open Port 25565 for Your Minecraft Server (and What to Do About CG-NAT)

Which port you need to open

Minecraft Java uses port **25565 TCP**. It's the one set by server-port in server.properties: if you changed it, open that one instead. You don't need UDP to play.

UDP only comes in if you use something extra: Bedrock (the Bedrock dedicated server, or Geyser so people can join from phones and consoles) uses 19132 UDP, and the Simple Voice Chat mod or plugin uses 24454 UDP. Each one is another rule on the router.

This guide is for a real server (the server.jar or a Paper server) running on your PC. If you don't have one yet, start with how to make a Minecraft server.

Step 1: give your PC the same home IP every time

The router hands out the IPs inside your home however it likes, and the port rule points at one of them: if your PC gets a different one tomorrow, the rule points at nothing.

1. Look up your IP and the router's

   On Windows, open “Command Prompt”, type ipconfig and note two lines for your connection: “IPv4 Address” (your PC's, something like 192.168.1.35) and “Default Gateway” (the router's, almost always 192.168.1.1 or 192.168.0.1).

2. Reserve it on the router

   On the router, look for “DHCP”, “Static IP” or “Address Reservation” and assign that IP to your PC. That way it doesn't change even when you restart.

Step 2: the rule on the router

1. Sign in to the router

   Type the gateway into your browser (for example 192.168.1.1). The username and password are usually on the sticker underneath the router. Some ISPs handle this from their app or customer area instead of this page.

2. Find the section

   Every brand calls it something different: “Port Forwarding”, “NAT”, “Virtual Servers” or “Port Mapping”. Sometimes it's inside “Advanced” or “Security”.

3. Create the rule

   Protocol TCP, external port 25565, internal port 25565 and, as the destination, your PC's IP from step 1. Give it a name (Minecraft) and save.

4. If the router asks, restart it

   Many apply the rule right away; others not until they restart.

Step 3: the Windows firewall

The first time you start the server, Windows asks whether to let Java use the network. Tick “Private networks” and press “Allow access”. If you closed it or said no, the router lets the connection through and Windows drops it.

To fix it: “Windows Defender Firewall” → “Allow an app or feature through Windows Defender Firewall”, and tick the Java that runs the server (“OpenJDK Platform binary” or “Java(TM) Platform SE binary”). If you have an antivirus with its own firewall, you also have to allow it there.

Step 4: check it can be seen from outside

1. Test the port from outside

   With the server running, open Is my port open? on the same PC or another one at home: it shows your public IP (the one you'll give your friends) and tests 25565 from our machine, the way a friend would connect. It tells you whether it's open, whether the router lets it through but the server doesn't answer, or whether nothing gets through.

2. Or test it with the IP

   If you already know your public IP (search “what is my IP”), you can also type it into Is my Minecraft server online?: if it shows as online, with its version and its MOTD, your friends can already join with that IP (with 25565 you don't need to add the port).

3. Don't test it from home

   Many routers don't let you reach your public IP from inside your own network. If it doesn't work for you, that doesn't mean it's closed: you join with localhost and leave the test to the tool or a friend.

If it's still closed: CG-NAT

Compare the public IP that “what is my IP” gives you with the one the router shows as “WAN IP” or “Internet IP” on its status page. If they aren't the same, or the router's starts with 100.64 to 100.127, you have CG-NAT: you share the IP with other customers of your ISP and no rule on your router can open anything, because your friend's connection is stopped earlier, at the ISP. Is my port open? does the comparison for you: type in the router's WAN IP and it tells you whether it's CG-NAT or there's another router in front.

It's common on home internet over 4G or 5G and on some fibre connections. In Spain, Digi uses it by default on its fibre and removes it with a separate paid service (check the conditions on its website). With other ISPs it's sometimes enough to call and ask for “a public IP” or to be “taken off CG-NAT”.

If you don't want to or can't, there are workarounds that don't go through the router: a VPN like Radmin or a tunnel like playit.gg (playing with friends without port forwarding), or a server outside your home (below).

Other reasons nobody can join

1. Two routers

   If you have your ISP's router and another one of your own behind it, you have to open the port on both (from the ISP's one to yours, and from yours to the PC), or put the ISP's one in bridge mode.

2. server-ip filled in

   In server.properties, server-ip has to be empty. With an address that isn't the machine's, the server won't start or won't listen where the connection arrives.

3. The server isn't running

   With the console closed there's nothing to answer: the port shows as closed even if the rule is fine. Check in the console that it has reached “Done”.

4. A different port

   If you changed server-port, the rule has to use that number, and your friends type it after the IP (yourip:25570).

5. Your friends connect but get kicked

   Then the port is already open: the problem is something else (version, whitelist, mods). It's covered in I can't connect to my Minecraft server.

What having the port open means

Your home IP is visible to whoever joins, and there are programs that scan the internet looking for open Minecraft servers: if it isn't for everyone, turn on the whitelist (whitelist) and leave online-mode set to true. And the world only exists while your PC is on: if you're not around, nobody plays.

What you notice most is your connection's upload speed and the PC's processor, which it shares with everything else you have open (including your own Minecraft if you play on the same machine).

Without touching the router: a server outside your home

On NapNodes there are no ports to open: every server has its own address (<id>.play.napnodes.com, without a port in Minecraft), it works with your PC switched off and your home IP doesn't show up anywhere. If you want voice chat or a web map, every Minecraft server comes with a second port already open in “Advanced settings” → “Ports”.

To try it, the free server: no card, you start it when you're going to play and it stops by itself when it's empty. If you stick around, you move to a plan with the same world.

Frequently asked questions