Common Minecraft server errors and how to fix them

This page lists the most common error messages from Minecraft servers and the game itself, with what they mean and how to fix them. The messages are quoted exactly as you'll see them, so you can simply search for them (Ctrl+F or the guide search).

How to read the log#

The server writes everything it does to the console and to files:

How to find the cause in the log:

1. Find the first line with ERROR or Exception – the errors after it are often just consequences.
2. Below the error is a stack trace (lines starting with at …). Look for a plugin or mod name in it – it's often visible in the package name, for example at com.example.mujplugin.….
3. If the trace contains Caused by: lines, the real cause is usually in the last of them.
4. WARN lines are warnings. The server usually keeps running and you don't need to deal with them unless something stops working.

You can download logs/latest.log in the Files tab with the Download button, or open it right in the editor.

You need to agree to the EULA in order to run the server. Go to eula.txt for more info.#

Cause: You haven't accepted the Minecraft license terms (EULA). The server shuts itself down right after starting.

Fix:

1. Open the Software tab.
2. In the Minecraft EULA block, click Accept and start.

On your own VPS, open eula.txt in the server folder and change eula=false to eula=true. Details are in the guide First start and the EULA.

**** FAILED TO BIND TO PORT!#

The full message:

**** FAILED TO BIND TO PORT!
The exception was: java.net.BindException: Address already in use
Perhaps a server is already running on that port?

Cause: Another program is already using the port the server is supposed to listen on.

Fix at StormHost: we set the server address and port automatically, so the cause is usually one of these:

• the previous server run hasn't finished yet – click Stop, wait half a minute and then click Start,
• a plugin or mod (web map, voice chat, Geyser) is set to the server's port – in its configuration, set a different port from the Network tab (Add port).

If the error persists, contact support.

Fix on your own VPS: find out what's using the port:

ss -tulpn | grep 25565

• ss -tulpn – lists listening TCP and UDP ports along with the programs using them.
• grep 25565 – keeps only the lines with port 25565 (use your own port).

Stop the other program (often a forgotten server that's still running), or use a different port.

A similar Address already in use error from Geyser means something else is running on the same UDP port, typically Query. See Crossplay with Bedrock.

java.lang.UnsupportedClassVersionError#

The full message looks like this, for example:

java.lang.UnsupportedClassVersionError: com/example/plugin/Main has been compiled by a more recent version of the Java Runtime (class file version 69.0), this version of the Java Runtime only recognizes class file versions up to 65.0

Cause: The server or a plugin needs a newer Java than the server runs on. The “class file version” numbers map to Java versions:

In the example, the plugin needs Java 25 (69), but the server runs on Java 21 (65).

Fix:

• The error comes from a plugin or mod: we pick Java automatically based on the Minecraft version (up to 1.16.5 Java 8, 1.17 Java 16, 1.18–⁠1.20.4 Java 17, 1.20.5–⁠1.21.x Java 21, 26.x Java 25). Download the plugin version made for your Minecraft version, or update the server to a newer Minecraft version (guide).
• The error comes from the server itself (the message names a server class, not a plugin class): the server probably wasn't installed through the Software tab. Use Software › Reinstall, or Import and pick the actual type and version – the customer area then sets the right Java.

Incompatible client! Please use …#

In older game versions, Outdated client! Please use … or Outdated server! I'm still on …. In the server list, the server shows Incompatible version! in red.

Cause: The player has a different game version than the server. The message ends with the version the server requires.

Fix:

• The player picks the same version as the server in their launcher (you can see the server version in the Software tab).
• To let players with a newer game version join, install the ViaVersion plugin on the server (Paper, Purpur). For players with an older version, add ViaBackwards as well.
• On modded servers, players need exactly the same game version, loader and mods.

Failed to connect to the server / Connection refused#

The server list shows Can't connect to server for the server.

Cause: Nothing is listening at the address and port you entered.

Fix:

1. In the Console tab, check that the server is running and that the console shows the line Done (…)! For help, type "help". You can't connect while the server is still starting.
2. Compare the address the player entered with the Connection address in the Network tab – including the port after the colon.
3. If the player connects through a domain, check the DNS records using the guide Server address and domain.
4. Check the server with the Minecraft Status tool.

Can't resolve hostname#

Cause: The game couldn't find the domain in DNS (a typo, a missing A record, or the change hasn't propagated yet).

Fix: Check the address and the DNS records using the guide Server address and domain. In the meantime, players can connect using the IP address and port from the Network tab.

Can't keep up! Is the server overloaded? Running 2500ms or 50 ticks behind#

Cause: The server can't keep up with the game. In the example, it's 2.5 seconds (50 ticks) behind.

Fix: A single message on startup or while new terrain is generating is fine. If it keeps repeating, the server is lagging. How to find the cause (spark, view distance, pre-generating the world) is covered in the guide Minecraft server performance.

java.lang.OutOfMemoryError: Java heap space#

Or the server shuts down without an error in the log (the last lines of logs/latest.log aren't about shutting down, Stopping server is missing) and the Console shows the lines Exit code: 137 and Out of memory: true.

Cause: The server ran out of memory. Java heap space means the heap is full: the server holds more data than fits (a large modpack, many players, a huge world), or a plugin or mod is leaking memory. A shutdown without an error means Java's total memory (the heap plus memory outside it) went over the plan's limit and the system stopped the server. OutOfMemoryError: Direct buffer memory or Metaspace points to a plugin or mod that hit the cap for network buffers or loaded classes.

Fix:

1. In the Startup tab, check the warnings next to the startup flags. If the heap is too large for the plan or the command has no memory caps, click Use recommended. After a plan change, the flags are recalculated automatically.
2. Run spark health in the console and watch the memory. If it stays almost full even after garbage collection, run spark heapsummary – it shows what's using the memory.
3. If it's just normal load, move to a bigger plan in the Change plan tab.

Details are in the guide Minecraft server performance.

Failed to verify username!#

The player may also see Failed to log in: Invalid session (Try restarting your game and the launcher) or Authentication servers are down. Please try again later. Sorry! in the game.

Cause: The server (with online-mode=true) couldn't verify the player's account with Microsoft. The player's login has expired, the authentication servers are down, or the player isn't using a genuine copy of the game.

Fix:

• The player fully closes the game and the launcher, signs out, signs back in and tries again.
• If the authentication servers are down, wait.
• We don't recommend turning off online-mode – it would let anyone in under any name (why).

You are not white-listed on this server!#

Cause: The whitelist is on and the player isn't on it. Since version 26.3, the whitelist is on even on a newly created server.

Fix: In the console, type whitelist add <NICK> (replace <NICK> with the player's name, without the angle brackets). Add Bedrock players with fwhitelist add <NICK>. You can turn the whitelist off in the Server properties tab (Whitelist). Details are in the guide Whitelist, operators and bans.

Multiplayer is disabled. Please check your Microsoft account settings.#

Cause: The player's account isn't allowed to play multiplayer (typically a child account or Xbox privacy settings).

Fix: The player (or a parent) allows multiplayer in the Microsoft / Xbox account settings. There's nothing to change on the server.

Expired profile public key. Check that your system time is synchronized, and try restarting your game.#

Cause: The player's computer has the wrong time.

Fix: The player turns on automatic time in their system settings and restarts the game.

The server is full!#

Cause: As many players are connected as max-players allows.

Fix: Raise Maximum players in the Server properties tab and restart the server. Keep performance in mind – more players means more load.

Could not load 'plugins/….jar' in 'plugins'#

Similar messages are Could not load plugin '….jar' in folder 'plugins' and, in older versions, Could not load 'plugins/….jar' in folder 'plugins'. Below the message there's usually more detail, most often:

org.bukkit.plugin.UnknownDependencyException: Unknown/missing dependency plugins: [Vault]. Please download and install these plugins to run 'MujPlugin'.

Cause: The plugin needs another plugin (a dependency) that's missing from the server – Vault in this example.

Fix: Install the missing plugin named in the square brackets. When you install through the Plugins tab, required dependencies are offered automatically. Other causes of this message: a damaged file (download it again), a plugin for a different server type (a Fabric mod in the plugins folder) or for a different Minecraft version. More in the guide Installing plugins.

Error occurred while enabling … (Is it up to date?)#

Cause: The plugin loaded but crashed while being enabled. Most often it's made for a different Minecraft version, has a configuration error, or couldn't connect to its database.

Fix:

1. Below the message, find the last Caused by: line – it tells you what happened.
2. Check that the plugin version supports your server version (the Plugins tab › Check for updates).
3. A configuration error (.yml): it usually shows up as the words YAML, ScannerException or mapping values are not allowed here with a line number. Fix the indentation (spaces only) or delete the plugin's configuration file – a default one is created on the next start.
4. A database error: see MySQL for plugins.

Mods: Incompatible mods found!#

A Fabric server won't start and below the message you see, for example:

Incompatible mods found!
A potential solution has been determined, this may resolve your problem:
    - Install fabric-api, any version.

Cause: A mod needs another mod (often Fabric API) or a different Minecraft or loader version. Fabric prints the exact fix (Install …, Replace …, Remove …).

Fix: Do what Fabric suggests. A line in the form <MOD> requires <VERSION> of <DEPENDENCY>, which is missing! tells you what's missing.

Mods: Attempted to load class … for invalid dist DEDICATED_SERVER#

Cause: The server has a mod meant only for the game (the client) – for example a minimap, shaders or a menu tweak. The server can't load it.

Fix: Find the mod's name in the message or in the crash report and remove it from the mods folder (or in the Mods tab). Players install client-side mods only in their own game. More in the guide Mods and modpacks.

Mods: players get kicked with a list of mods when joining#

Cause: The player doesn't have the same mods, or the same mod versions, as the server.

Fix: Players need the same modpack in the same version as the server. They download the modpack from the same source (Modrinth, CurseForge) and pick the same version.

Corrupted chunk: Failed to read chunk [x, z]#

Other similar messages: Region file … has truncated header, Failed to read chunks from region file ….

Cause: Part of the world is corrupted, most often after a server crash or an unfinished save.

Fix:

1. The safest option is to restore a backup from the Backups tab (guide).
2. Without a backup, you can delete just the damaged region file. A region is a file r.<X>.<Z>.mca, where <X> and <Z> are the chunk coordinates from the message divided by 32 and rounded down (chunk [70, -5] is in r.2.-1.mca). You'll find it in the world/dimensions/minecraft/overworld/region folder (since version 26.1), or in world/region in older versions.

The message Chunk file at [x, z] is in the wrong location; relocating. isn't an error – the server moved the chunk to the right place on its own.

Failed to load datapacks, can't proceed with server load.#

Cause: A datapack in the world is damaged or made for a different Minecraft version (often after a version change).

Fix: In the Files tab, open the world/datapacks folder, move the faulty datapack somewhere else (or delete it) and start the server. The lines above the message tell you which one it is. If you're not sure, restore a backup from before the version change.

Timed out / Connection Lost#

Cause: The connection between the game and the server dropped. Either on the player's side (Wi-Fi, mobile data), or the server froze for a moment and didn't respond in time.

Fix:

• Only one player was disconnected: the problem is their connection. They can try a cable or a different network.
• Everyone was disconnected at once: the server froze. Look in the console for Can't keep up! or watchdog messages (see below) and follow the guide Minecraft server performance.

The server freezes and shuts down: A single server tick took 60.00 seconds (should be max 0.05)#

This is what it looks like on Vanilla, Fabric and NeoForge. It's followed by Considering it to be crashed, server will forcibly shutdown.

On Paper and Purpur, freezes are watched by their own watchdog and the messages are different. After just 10 seconds of freezing, --- DO NOT REPORT THIS TO PAPER - THIS IS NOT A BUG OR A CRASH is printed repeatedly with a dump of the main thread. When the freeze lasts 60 seconds, a block starting with The server has stopped responding! This is (probably) not a Paper bug. is printed with a thread dump, and the server shuts down.

Cause: A single tick took more than 60 seconds, the server decided it had frozen and shut down. The limit is set by max-tick-time in server.properties (Vanilla, Fabric, NeoForge), and on Paper and Purpur by settings.timeout-time in spigot.yml. Most often a plugin is waiting for a database or the internet on the main thread, or there's a huge redstone build or thousands of TNT exploding.

Fix: In the thread dump, find the Server thread (on Paper, the Server thread dump block) and look for a plugin or mod name in it. Update or remove that plugin. Don't raise or disable the limit – a frozen server would then hang for a long time or forever.

Console: Unknown or incomplete command. See below for error#

Cause: The command doesn't exist (a typo), or it belongs to a plugin that didn't load.

Fix: Check the command name and the spot marked <--[HERE] below the message, where the error is. In the console, commands are typed without a slash. You'll find a list of commands in the guide Console and commands.

Customer area: The flags are not compatible, reverted to the previous settings.#

Cause: The server didn't start with the new startup flags, so the customer area reverted them.

Fix: In the Startup tab, check Custom flags (a typo, a flag for a different Java version) or pick the default Recommended (G1) preset. More in the guide Minecraft server performance.

If it still doesn't work#

Contact us and send:

• the service ID or server name (you'll find it in My services),
• what you did right before the error (an update, a new plugin, a version change),
• the logs/latest.log file (download it in the Files tab) and, if there is one, the newest file from the crash-reports folder,
• for lag, a link to the profile from spark profiler start --timeout 600,
• the exact time the error happened.

Never send passwords or the contents of key.pem or forwarding.secret.

Further reading#

• Server on the Minecraft Wiki (opens in a new window)
• Paper documentation (opens in a new window)
• Profiling with spark (opens in a new window)