Let's face it: errors are annoying. In this article, we will guide you in interpreting and fixing an error on your Minecraft server.

In this guide, we will separate the most common errors into the categories of startup, minor, and connection errors. Find your error here based on when it happens and what gametype you are using.
I. Startup errors
General errors
EULA error
When first starting your server, you will need to accept the Minecraft EULA (basically their terms of service).
It will throw the error and crash once upon startup saying, You need to agree to the EULA in order to run the server. Go to eula.txt for more info.
A window should pop up asking you to accept Minecraft EULA. Either press "I agree" there, or navigate to eula.txt in the file manager and set eula to true.
Permission denied
If you are experiencing an error such as /entrypoint.sh: line 12: ./bedrock_server: Permission denied, then you must navigate to the file indicated by the error, right-click or click the three dots next to the file, go to permissions, and change the number to 755.
Failed to bind port
When this happens, you will most likely receive an error such as:
The exception was: java.net.BindException: Address already in use
Perhaps a server is already running on that port?

To fix this, you will need to change your server port because the one you want is being used by another server. If you have a dedicated IP, open a live chat for this one.
Unable to read world format
When you have an error about the server not being able to load the world file, it means that either your world is corrupted or not compatible with your gametype. For example, don't attempt to use a Java world on a Bedrock server. To fix this, you can let the server generate its own world by deleting your current world file, convert the world to a different format if you have the tools for it, or import a new non-corrupted and compatible world.

Java errors
Unable to access server.jar file error
This error is quite common. It means that your server.jar file is either missing, named wrong, or not understandable. If your server file is named something like paper-1.17.3-21.jar, make sure to rename it server.jar. If your server file is missing or corrupted, make sure to either upload/re-upload it manually or reinstall your server. This also applies to the Error: Invalid or corrupt jarfile server.jar error.
Java version error
It's easy to notice this error if you see something like this on the console: Minecraft 1.17 requires running the server with Java 16 or above. Download Java 16 (or above) from https://adoptopenjdk.net/ or Unsupported Java detected (60.0). Only up to Java 13 is supported.
However, if you're running Forge, for example, it's a little harder to notice. You can tell it's a Java version error when you see a bunch of errors resembling this:

Forge Java version startup error
To fix this error, go to startup on the control panel and change to the appropriate Java version on the top right. (Java 8-11 until 1.17. For 1.17+ use Java 16-17)
Crash: out of memory
When your server freezes, everyone is kicked, and the console is not responding, it's most likely because your server has passed its RAM limit. When this happens, stop the server (you may have to wait a few minutes for it to stop) or kill it if you're impatient (not recommended). Always make sure to allocate the necessary RAM for your server, optimize its memory consumption, and restart it when the RAM gets high.
Crashing mods/plugins
If your startup error is not one stated in this section, it is most likely an error originating from one of your server's mods or plugins. Locate the mod/plugin that is mentioned in the error and either find an updated/fixed version or delete it.

Bedrock errors
Failed to open curl lib from binary
When you receive this error it means your ipv4 and ipv6 are the same. Simply change the ipv6 to another port in server.properties to fix it.
For most Pocketmine startup errors, make sure you have the right PHP version for your version. You can change it in startup.
Nukkit errors
Make sure to choose your language upon startup, which can be mistaken for the server not starting. For example, for English type eng.

Proxy errors
Make sure backends are configured properly:
bukkit.yml connection-throttle to -1
spigot.yml bungeecord to true
server.properties online-mode to false
IP forwarding to true on bungee

Then restart all related servers

II. Minor errors
General errors
Plugin/mod errors
When you receive an error that doesn't prevent the server from starting, it's probably a mod or plugin problem. The plugin/mod will then most likely be disabled or not work properly. The problem could originate from a problem in its configuration (check the site you downloaded it from for instructions), but it could also be because it's outdated or just badly made. Check the configuration, in particular if the error points to one setting, get an updated version, or just delete it if it never worked.

Java errors
Missing required core mod or plugin
If your console is showing this error, it means that you have a mod/plugin that requires a missing core mod/plugin. To fix this, either remove the dependent mod/plugin or install the mod/plugin it requires to run (it will say on the console or on the site you downloaded it from).
Can't keep up, is the server overloaded?
During this error, you will find a TPS (ticks per second) drop, meaning lag. To fix this, you will need to locate the source of the lag (see our server optimization article).

Pocketmine errors:
Incompatible protocol version
When a plugin has an incompatible protocol version, it means it is outdated. If you download your plugins from Poggit, make sure to select the right version for your server on the plugin page (top right).
Failed loading error
Failed loading /home/container/bin/php7/lib/php/extensions/no-debug-zts-20190902/opcache.so: /home/container/bin/php7/lib/php/extensions/no-debug-zts-20190902/opcache.so: cannot open shared object file: No such file or directory: you can ignore this, it will not affect your server at all.

III. Connection errors
General errors
Outdated server
This means your server is running an older version of Minecraft than the one you are trying to connect with. Either update your server, downgrade your Minecraft client, or add a multi-version support plugin such as ViaVersion.
Outdated client
This means your server is running a newer version of Minecraft than the one you are trying to connect with. Either downgrade your server, update your Minecraft client, or add a multi-version support plugin such as ViaBackwards (requires ViaVersion).
Invalid IP
This means you entered something other than an IP in the server address field when adding the server. Make sure you put in an IP with numbers and dots.
Banned by an operator
🔨 You've been banned! Contact a server administrator to have them unban you. If you have console access, use /pardon or /unban. If your IP is banned, use /pardon-ip or unban-ip.
The server is whitelisted
Add your in-game name to the whitelist with whitelist add on the console. You can also turn off whitelist with whitelist off or by changing whitelist to false in server.properties and restarting the server.
Bad login
Make sure you're not attempting to log in too fast, and that you're using a Minecraft version that is compatible with the server. This could also be caused by a bad internet connection.
The authentication servers are currently down for maintenance
This error, or com.mojang.authlib.GameProfile ... lost connection: Disconnected could mean a few things. The authentication servers could really be offline (in that case, wait), or your firewall could be blocking the connection. In that case use this tutorial. If this doesn't fix itself, consider changing online-mode to false in server.properties, allowing anyone to join.

Java errors
Failed to Verify Username/Invalid session
When you get this error, it means you need to log back in. Log out of your Minecraft launcher then log back in again. If you're using a non-premium version of Minecraft, make sure to set online-mode to false in server.properties and restart your server.
Connection refused
First, check if other players are having this problem.
If it's just you:
・Make sure you're using the correct IP and port.
・Make sure your antivirus or firewall aren't blocking the connection.
・Make sure your network is strong and not blocking the 25565 port.
If it's not just you:
・Check the server console for errors, make sure your server is set to a compatible gametype.
This means your computer/internet cannot handle connecting to the server. Consider using a stronger computer, closing other programs, or getting better bandwidth.
java.net.SocketException: Connection reset
This could be caused by your internet or errors/intensive computing on your server. Check your server console for errors.
java.io.IOException: Server returned HTTP response code: 503
This happens when Minecraft.net is down. Wait, and keep up with Minecraft news (through social media).
This means your Minecraft client has crashed. Try to find the Java crash log to identify the issue (named something like hs_err_pid...txt on your desktop). Worst case scenario you will have to rename the .minecraft folder and relaunch Minecraft so that it creates a new folder (then copy your Minecraft saves there).

Bedrock errors
Unable to connect to world
Make sure you're putting in the correct IP and port. If you are, make sure your server is set to a compatible gametype and check for console errors that could be interfering with your connection.
You need to authenticate to Microsoft services
To fix this error, simply reload Minecraft, log out and log back in to Minecraft using your Microsoft account. It should then be fixed. If not, it could be because authentication servers are down and you need to wait.

Pocketmine errors
Internal server error
This error will kick players out of a Pocketmine server, or even force it to stop. It's often caused by a plugin, so identify which one by looking at the error on the console and checking its configuration and version. Always make sure your plugins work and are compatible with your server.

Not finding your error? Try to understand the cause by reading your logs or crash report.

IV. Reading a crash report
In file manager, you can sometimes find crash reports in a server named crash reports. There, you will find many reports, each with a date. Navigate to the day of the crash. The log there will show the error(s) leading up to the crash as well as system details. For this section, it is good to know what each of these letter mean: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
Here's an example:
| State | ID | Version | Source | Signature |
|:----- |:---------- |:------------ |:-------------------------------- |:--------- |
| L | minecraft | 1.12.2 | minecraft.jar | None |
| L | mcp | 9.42 | minecraft.jar | None |
| L | FML | | forge1122.jar | None |
| L | forge | | forge1122.jar | None |

V. Other errors
The first thing to do when no fixes work is to try reinstalling (make a backup first).

For special joining problems, consult the Minecraft help forum or contact Minecraft support.
If you still cannot fix your error, open a live chat 👍
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