When friends can't join, the server is usually offline or asleep, the address or port is wrong, or their game version or edition doesn't match. Check those three first. Then work through the whitelist, the player limit, mods, account errors and, for a home server, your network.
Join problems feel random, but the error message and the order you check things in usually point straight at the cause. Start at the top: the first causes are the most common and take seconds to rule out.
1. The server is offline or asleep
Most free and budget hosts stop a server when nobody is playing. Your friend sees the server as offline, or the connection simply times out, because there is nothing running to join.
Check: open your host’s panel. If the server is stopped, start it and wait until the panel says it is online before anyone connects.
Fix for good: give the people who play most a way to start it themselves, or use a host that starts the world when someone joins.
On Aternos: the server stops when nobody is online
Aternos says plainly that it stops empty servers to share limited resources. A countdown in the server panel shows when an empty server will stop; once a player is online the timer disappears, and it starts again when the last player leaves. When starting, a free server can also wait in a queue.
So “Aternos server not letting me join” usually means the server is not running. You have two official ways to fix that:
- Share access. The owner adds a friend under Access with the Start permission, and the friend starts the server from their own Aternos account. Aternos’s share-access article warns to grant access only to people you fully trust.
- Autostart through Dawn Launcher. If you join an offline Aternos server through Aternos’s own Dawn Launcher, the server starts automatically, as long as the owner hasn’t disabled it in the options. Friends who use a different launcher still find the server offline.
For a wider look at how free hosts handle sleeping servers, see free Minecraft server hosting without the start button.
2. The address or port is wrong
One wrong character, an old address, or a missing port sends your friend to the wrong place.
Check: copy the address exactly as your host shows it, including any port after the colon. Java Edition uses port 25565 by default, so most Java addresses need no port. Bedrock Edition uses 19132 by default and asks for the port in a separate field.
If your host gives you a different address for Bedrock players, make sure they use that one. Re-share the address after any server move. Some hosts change it when a server is recreated.
3. Their game version doesn’t match the server
“Outdated client” or “Outdated server” means the friend’s game and the server run different Minecraft versions.
Check: compare the version in the server panel with the version on the friend’s launcher or console. Java players can choose an older version under Installations in the launcher. Bedrock players generally have to be on the current version, so the server must keep up.
4. They play a different edition
Java Edition and Bedrock Edition (consoles, phones, tablets and the Windows Bedrock app) cannot join each other’s servers on their own. A Java server needs a translation layer such as Geyser for Bedrock players to connect.
Check: ask your friend where they play. If you have a mix, read can Java and Bedrock play together? before you change anything.
Console Bedrock players also cannot add a custom server from the Servers tab without a workaround, so check your host’s console instructions.
5. They aren’t on the whitelist
“You are not white-listed on this server” is the clearest error there is: the whitelist is on and your friend’s name isn’t on it.
Check: add the exact Java username, or the Xbox gamertag for Bedrock players, then try again. Names are case-sensitive on some setups, and a renamed account needs re-adding. Our whitelist and anti-grief guide covers setting it up safely.
6. “Failed to verify username”
This means the server could not confirm your friend’s Minecraft account session with Microsoft. It is an account and login problem, not a whitelist one.
Check: have the friend close the game and launcher completely, sign out and back in, and try again. If many people see it at once, Microsoft’s login services may be having trouble, and waiting is the only fix.
Do not switch the server to offline mode to get around it. Offline mode stops the server checking accounts at all, so anyone can join with any name, including yours.
7. The server is full
“The server is full” means the player limit is reached. Free tiers often cap players low.
Check: look at the max-players setting and how many people are online. Raise the limit only if the plan has the memory for it. Our RAM guide shows what a bigger group needs.
8. Mods or plugins don’t match
On a modded server, every player needs the same mod loader, the same mods and compatible versions. Errors such as “mismatched mod channel list” or a list of missing mods mean the friend’s game and the server don’t match.
Check: share the exact modpack and version with the group, ideally through the same launcher profile. Plugins on a Paper server don’t need installing by players, but a broken plugin can still stop people joining, so check the server log after a failed join. Our mods and modpack setup guide covers matching everyone’s game to the server; if you are still choosing a setup, see plugins vs mods.
9. Your network blocks them (home servers only)
If you host on your own computer, friends outside your home need your router to forward the server port to that computer, and your firewall must allow it. Some internet providers place customers behind shared addresses (CGNAT), which blocks incoming connections no matter what you forward.
Check: can someone on your own Wi-Fi join using your local address, while outside friends can’t? Then it is the network. The self-hosted vs paid server guide explains when it is easier to move to a host.
Can a server start automatically when a friend joins?
Only if the host supports it. A normal server has to be running before anyone can connect, which is why so many friend groups end up texting “can you start the server?”.
Some hosts now handle this for you. Aternos does it when you join through its Dawn Launcher. Hosts with join-to-wake start the world when a friend connects to the usual address from the regular game, with no special launcher and no one needing panel access.
Quick checklist
- Is the server running? Start it, or use a host that wakes on join.
- Is the address, and the port for Bedrock, copied exactly?
- Do the game version and the server version match?
- Same edition, or a cross-play setup for mixed groups?
- Is the friend on the whitelist with their exact name?
- Account error? Restart and sign back in; never use offline mode.
- Is there room under the player limit?
- Same mods and versions as the server?
- Home server? Check port forwarding, firewall and CGNAT.
If you are setting up a new world for the group, start with how to make a Minecraft server for friends.