# Common Issues

***

## 1. Minecraft Authentication Issues

**Minecraft Error Messages:**

```
Failed to verify username!
Failed to authenticate user: Invalid session (Try restarting your game and the launcher)  
```

**Explanation:**\
This error occurs when a Minecraft server is running in **online mode**, which requires players to have a valid **Minecraft: Java Edition** account purchased from Mojang/Microsoft. If a user does not own an official copy of the game or the authentication servers are temporarily down, they will not be able to join.

**Solution:**\
If you want to allow players without an official Minecraft account (cracked clients) to join your server, you must disable online authentication.

1. **Locate `server.properties` File:**
   * Navigate to your server’s root folder.
   * Find the file named `server.properties`.
2. **Modify Online Mode Setting:**
   * Open `server.properties` with a text editor.
   * Find the line:

     ```
     online-mode=true
     ```
   * Change it to:

     ```
     online-mode=false
     ```
3. **Save and Restart the Server:**
   * Save the file.
   * Restart your server for the changes to take effect.

{% hint style="danger" %}
Disabling **online mode** allows players with non-premium accounts to join but **disables Mojang’s authentication system**, making your server more vulnerable to impersonation and security risks. To improve security, consider installing plugins like **FastLogin** or **AuthMe** to require password authentication for players.
{% endhint %}

***

## **2. Java Issues - Server Crash On Start**

**Console Message**:

```
Minecraft 26.1 and newer requires running the server with Java 25 or above. For information on how to update Java, see https://docs.papermc.io/misc/java-install
```

or the following message immediately after starting the server:

```
Error: A JNI error has occurred, please check your installation and try again.
Exception in thread "main" java.lang.UnsupportedClassVersionError: net/minecraft/server/MinecraftServer has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0
```

or the following message immediately after starting the server:

```
The server either closed or crashed...
The server will restart after the countdown, please close this window to stop the server completely.
```

**Explanation**:\
This error means that the Minecraft server requires a newer version of Java, typically **Java 21** for Minecraft 1.20.5 and above or **Java 25 for Minecraft 26.1** and above, but your system is running an older version like Java 8 or Java 11.

**Solution** (for Windows):

* [Check out this guide.](/b.-setups/information/common-issues/java-version-check-and-update-install-guide.md)

***

## 3. Server Logo or Resource Pack Items Not Loading

**Symptoms:**

* The server logo (server icon) does not appear in the server list
* Custom resource pack textures are missing
* Custom items appear as default Minecraft textures
* Server resource pack is not downloaded when joining

**Explanation:**

Some Minecraft servers use a **server resource pack** to add custom textures, items, fonts, or models. If the client is not configured to accept server resource packs, Minecraft will not download or load these assets.

In some cases, certain font settings (such as **Force Unicode Font**) can also cause resource pack elements to display incorrectly.

***

**Solution** (for Windows):

1. **Enable Server Resource Packs**

* Before joining the server:
  1. Open the **Multiplayer** server list.
  2. **Left-click the server once** (do not join yet).
  3. Click **Edit** in the bottom-left corner.
  4. Find the setting **Server Resource Packs**.
  5. Set it to either:
     1. **Enabled** - automatically downloads the pack
     2. **Prompt** - asks before downloading
* Then click **Done** and join the server again.

2. **Disable Force Unicode Font**

* Some resource packs require the default Minecraft font rendering.
* Open the following settings:
  * **For newer Minecraft versions:**

    ```
    Options > Language > Font Settings > Force Unicode Font: OFF
    ```
  * **For older Minecraft versions:**

    ```
    Options > Language > Force Unicode Font: OFF
    ```
* After changing the setting, reconnect to the server.

***

## **4. Insufficient Resources**

**Console Message**:

```
[17:22:31 ERROR]: Exception in server tick loop
java.lang.OutOfMemoryError: Java heap space
    at net.minecraft.server.MinecraftServer.loadWorld(MinecraftServer.java:721)
    at net.minecraft.server.dedicated.DedicatedServer.init(DedicatedServer.java:305)
    ...
```

**Explanation**:\
This error occurs when the server doesn’t have enough RAM to function. By default, the server may allocate only 2GB of RAM, which is insufficient for larger servers, modded worlds, or multiple players.

***

**Solution** (for Windows):

1. **Modify the Server Startup Script**:
   * Open the **start.bat** file in your server folder.
   * Edit the file to allocate more memory by changing the `-Xmx` and `-Xms` parameters:

     ```bat
     java -Xmx6G -Xms4G -jar paper-1.21.4.jar
     ```

     Here, `-Xmx6G` sets the maximum RAM to 6GB, and `-Xms4G` sets the initial allocated RAM to 4GB.
2. **Ensure Sufficient System Memory**:
   * Right-click **This PC** > **Properties** and check how much RAM your system has. Make sure the server’s allocated RAM doesn’t exceed your system's total available memory.
3. **Command Line Check**:
   * If the server still crashes, open **Command Prompt** and run:

     ```bash
     tasklist | findstr java
     ```

     This will show how much memory the Minecraft server is using in real time.

***

## **5. "Can't Keep Up!" Warning**

**Console Message:**

```
[17:22:31 WARN]: Can't keep up! Is the server overloaded?
Running 5000ms behind, skipping 100 tick(s)
```

**Explanation:**

This warning appears when the Minecraft server is unable to keep up with the normal game tick rate. Minecraft servers are designed to run at **20 ticks per second (TPS)**. When the server’s CPU cannot process all game logic fast enough, it falls behind and begins skipping ticks.

This usually happens when:

* Too many players are online
* Too many entities (mobs, animals, dropped items)
* Too many plugins or mods
* The view-distance is set too high
* The server CPU is too weak
* The world is generating new chunks

When the server falls behind, players may experience:

* lag
* delayed block breaking
* mobs freezing or teleporting

***

**Solution** (for Windows):

**1. Reduce View Distance**

* Open the **server.properties** file in your server folder and lower the view distance:

  ```
  view-distance=8
  simulation-distance=6
  ```
* Lower values reduce the number of chunks loaded for each player and improve performance.

**2. Allocate More RAM**

* Open the **start.bat** file in your server folder and increase the memory allocation.

  ```
  java -Xmx6G -Xms4G -jar paper-1.21.4.jar
  ```

Here, `-Xmx6G` sets the maximum RAM to 6GB, and `-Xms4G` sets the initial allocated RAM to 4GB.

**3. Reduce Entities**

* Large numbers of mobs or dropped items can cause lag.
* You can:
  * remove entities with server commands
  * install optimization plugins such as **ClearLag**
* Example command (this will remove all dropped items on the ground):

  ```
  /kill @e[type=item]
  ```

***

## **6. Port Already in Use**

**Console Message**:

```
[17:22:31] [Server thread/WARN]: **** FAILED TO BIND TO PORT!
[17:22:31] [Server thread/WARN]: The exception was: java.net.BindException: Address already in use: bind
[17:22:31] [Server thread/WARN]: Perhaps a server is already running on that port?
```

**Explanation**:\
This error means that another application (or another Minecraft server instance) is already using the default server port (**25565**). A port can only be used by one process at a time.

***

**Solution** (for Windows):

1. **Check for Other Processes Using the Port**:
   * Open **Command Prompt** as Administrator and run the following command to see if any process is using port 25565:

     ```bash
     netstat -aon | findstr :25565
     ```

     This will list any processes using port 25565. The last number is the **PID** (Process ID).
2. **Terminate the Conflicting Process**:
   * If a process is using the port, find it by running:

     ```bash
     tasklist | findstr <PID>
     ```
   * Terminate the process by running:

     ```bash
     taskkill /F /PID <PID>
     ```
3. **Change the Server Port**:
   * If you cannot free up port 25565, open the `server.properties` file and change:

     ```properties
     server-port=25566
     ```
   * Save the file and restart the server.

***

## **7. Firewall or Network Issues**

**Minecraft Error Message After Trying To Connect To The Server:**

```
Timed out
```

**Explanation**:\
This error means that a player was unable to connect to your server. It could be due to your firewall blocking connections or incorrect port forwarding. On a local machine, firewalls sometimes block external traffic from reaching the server.

***

**Solution** (for Windows):

1. **Allow Minecraft Server Through Windows Firewall**:
   * Open **Control Panel** > **System and Security** > **Windows Defender Firewall** > **Allow an app or feature through Windows Defender Firewall**.
   * Find `javaw.exe` in the list and ensure it's allowed for both **Private** and **Public** networks. If it's not there:
     * Click **Allow another app** > **Browse** > navigate to your Java installation folder (`C:\Program Files\Java\jdk-21.x.x\bin`) and select `javaw.exe`.
2. **Port Forwarding** (for home routers):
   * Open your router settings (usually accessed via a browser at `192.168.1.1`).
   * Go to **Port Forwarding** settings and forward TCP port **25565** (or whichever port your server uses) to your machine’s local IP (e.g., `192.168.1.101`).
3. **Verify Your Public IP**:
   * If you are hosting the server on a home network and allowing external players, provide them with your **public IP**. You can check your public IP by visiting [WhatIsMyIP](https://www.whatismyip.com).

***

## **8. Incorrect EULA**

**Console Message**:

```
[17:22:31 INFO]: You need to agree to the EULA in order to run the server. Go to eula.txt for more info.
```

**Explanation**:\
The Minecraft server requires you to accept the **End User License Agreement (EULA)** before it can start. If `eula=false` in the `eula.txt` file, the server won’t run.

***

**Solution** (for Windows):

1. Open the `eula.txt` file in the server directory using **Notepad**.
2. Change the line:

   ```properties
   eula=false
   ```

   to:

   ```properties
   eula=true
   ```
3. Save the file and restart the server.

***

## **9. Common Plugin Errors**

### **9.1. Incompatible Plugin Version**

**Console Message**:

```
[17:22:31 ERROR]: Could not load 'plugins/WorldEdit.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: Unsupported API version 1.20
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:132)
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:398)
    ...
```

**Explanation**:\
This error occurs when a plugin is designed for a different version of Minecraft than the server is running. For example, the server might be running **Minecraft 1.18**, but the plugin was made for **Minecraft 1.20**.

***

**Solution** (for Windows):

1. **Check Plugin Compatibility**:
   * Go to the plugin’s page (usually on sites like [SpigotMC](https://www.spigotmc.org) or [Bukkit](https://dev.bukkit.org)) and verify which Minecraft versions the plugin supports.
2. **Download the Correct Version**:
   * If an older or newer version of the plugin is available for your Minecraft version, download that version and place it in the `plugins` folder.
3. **Update the Server**:
   * If you prefer to use the newer plugin version, consider updating your server to match the plugin’s version. Always ensure your plugins and server are compatible.

***

### **9.2. Missing Dependencies**

**Console Message**:

```
[17:22:31 ERROR]: Could not load 'plugins/EssentialsX.jar' in folder 'plugins'
org.bukkit.plugin.UnknownDependencyException: Vault
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:219)
    ...
```

**Explanation**:\
This error occurs when a plugin requires another plugin (known as a **dependency**) to function, but the dependency is not installed. In this example, the **EssentialsX** plugin requires **Vault** to be installed.

***

**Solution** (for Windows):

1. **Identify the Missing Dependency**:
   * Check the error log to find out which dependency is missing (e.g., Vault in the above error).
2. **Download the Dependency**:
   * Go to the plugin repository (e.g., [Vault](https://www.spigotmc.org/resources/vault.34315/)) and download the latest compatible version of the missing plugin.
3. **Install the Dependency**:
   * Place the downloaded plugin in the `plugins` folder.
   * Restart your server to load the new dependency.
4. **Check Plugin Documentation**:
   * Some plugins require additional configuration or dependencies. Always review the plugin’s official documentation to ensure all necessary dependencies are installed.

***

### **9.3. Plugin Configuration Error**

**Console Message**:

```
[17:22:31 ERROR]: Could not pass event PlayerJoinEvent to MyPlugin v1.0
org.bukkit.event.EventException: null
    at org.bukkit.plugin.EventExecutor$2.execute(EventExecutor.java:72)
    ...
Caused by: java.lang.NullPointerException
    at myplugin.MyPlugin.onPlayerJoin(MyPlugin.java:42)
    ...
```

**Explanation**:\
This error occurs when a plugin encounters an issue during runtime, often due to an incorrect configuration file, missing settings, or a code issue within the plugin itself.

***

**Solution** (for Windows):

1. **Check the Plugin’s Configuration**:
   * Open the plugin's configuration file (usually located in the `plugins/<plugin_name>` folder).
   * Look for any errors, missing fields, or invalid values.
2. **Revert to Default Config**:
   * If you’re unsure about the correct settings, delete the configuration file and restart the server. The plugin will generate a fresh default configuration file.
3. **Check for Plugin Updates**:
   * If the error persists, visit the plugin’s page and check if there’s an update or patch that fixes the issue.
4. **Report the Issue**:
   * If it seems like a plugin bug, report the error to the plugin developer, providing the error message and steps to reproduce.

***

## **10. General Minecraft Errors**

### **10.1. Corrupted World Files**

**Console Message**:

```
[17:22:31 WARN]: Chunk file at 45, 12 is in the wrong location; relocating. (Expected 45, 12, got 44, 11)
[17:22:31 ERROR]: Couldn't load chunk at 45, 12
java.io.IOException: Corrupted world data
    at net.minecraft.server.level.chunk.ChunkProvider.load(ChunkProvider.java:421)
    ...
```

**Explanation**:\
This error occurs when one or more chunks in your Minecraft world become corrupted, often due to improper shutdowns, crashes, or disk errors. The server can’t read the chunk data properly, which can cause issues when loading the world.

***

**Solution** (for Windows):

1. **Backup Your World**:
   * Before trying to fix the issue, make a backup of your world folder by copying it to a safe location.
2. **Use MCEdit to Repair**:
   * Download and install **MCEdit** (a world editing tool for Minecraft).
   * Open your world in MCEdit and locate the corrupted chunk. Delete or repair the chunk, and save the world.
3. **Delete the Corrupted Region File**:
   * Minecraft worlds are divided into **region files**, each containing a large set of chunks. Find the region file corresponding to the corrupted chunk and delete it. The server will regenerate it automatically:
     * World region files are located in `world/region/` and have names like `r.x.z.mca`. Use an online tool like [ChunkBase](https://www.chunkbase.com) to find the region containing the corrupted chunk.
4. **Restore From Backup**:
   * If repairing doesn’t work, restore the world from a previous backup before the corruption occurred.

***

### **10.2. "Internal Server Error" on Player Join**

**Console Message**:

```
[17:22:31 ERROR]: Player lost connection: Internal Server Error
java.lang.NullPointerException: Cannot invoke "net.minecraft.server.level.EntityPlayer.d()" because "<parameter>" is null
```

**Explanation**:\
This error often occurs when a player tries to join a server that has an issue with plugins, mods, or corrupted player data, resulting in the server disconnecting them due to an internal error.

***

**Solution** (for Windows):

1. **Check for Plugin or Mod Conflicts**:
   * Disable any newly installed or recently updated plugins or mods. You can do this by temporarily moving them out of the `plugins` or `mods` folder and restarting the server to see if the issue is resolved.
2. **Clear Player Data**:
   * If the issue seems specific to a player, you can reset that player’s data by deleting their player data file from the `world/playerdata/` folder. Be sure to make a backup of this file before deleting it.
3. **Review Logs**:
   * Check the server logs in the `logs/latest.log` file for more detailed information about what caused the error.

***

{% content-ref url="/pages/988mOw8xIx4Vsn0WzLKL" %}
[Further Assistance](/b.-setups/information/common-issues/further-assistance.md)
{% endcontent-ref %}


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