Minecraft server does not startRead the logs and fix the most common startup errors

Published on October 20, 2026

First: read the log

A Minecraft server almost always tells you itself why it does not start. The message is in the console in the web interface and also in the file logs/latest.log, which you can download via WebFTP or SFTP.

The reading direction is important: do not look for the last line, but for the first line with [ERROR] or Caused by:. Everything after that is usually a follow-up error. This one line usually answers the whole question.

• logs/latest.log - the log of the last start
• crash-reports/ - only for real crashes after a successful start
• Console in the web interface - follow the same output live

EULA not accepted

On the very first start, every Minecraft server deliberately stops and writes, in essence, that you have to accept the EULA. Afterwards, the file eula.txt sits in the server directory with the entry:

eula=false

Set the value to eula=true, save and restart. This confirms Mojang's end user licence agreement. In our web interface, the EULA is usually already set during setup - if the message appears anyway, check the file directly.

Wrong Java version

The second most common cause. Newer Minecraft versions require a specific minimum Java version; if an older one runs, the start aborts with an UnsupportedClassVersionError message. Typical wording in the log:

java.lang.UnsupportedClassVersionError: net/minecraft/server/Main
has been compiled by a more recent version of the Java Runtime

Which version is needed for what and how to switch it is described in the guide Change the Java version. Conversely, a Java version that is too new can also slow down old mod loaders - Forge installations for older Minecraft versions are sensitive here.

A plugin or mod blocks the start

If the server ran until yesterday and no longer starts after an installation, the cause is almost always the new file. The log then shows the name of the plugin or mod right before the error.

1. Remove the most recently added file from plugins/ or mods/ and restart.
2. If it starts again, it was that file - usually because of the wrong version for your Minecraft version.
3. If it still does not start, move half of the extensions out and keep halving until the culprit is found.

Often it is not a defect but a version gap: a plugin for 1.20 does not necessarily run on 1.21. Check the supported versions on the download page before you keep searching. How to add extensions cleanly is shown in Install plugins & mods.

Damaged world or configuration

After a hard abort, the world can be damaged. The log then shows references to the region files or to level.dat. Two routes:

• Restore a backup: the quickest route if you have a recent backup. Backups are self-service with us - how to create them is described in Create backups.
• Use level.dat_old: Minecraft keeps a previous version of the file. Copying it in place of level.dat often saves the world - back up the whole world folder first.

A broken server.properties can also prevent the start, for example through an invalid value. Which values are allowed is explained in server.properties explained.

Too little memory

If the server starts up and aborts shortly afterwards with OutOfMemoryError or Could not reserve enough space for object heap, the allocated RAM is not enough. This mainly affects modpacks, which need much more than vanilla.

How much is realistic for which server type is in the guide How much RAM does a Minecraft server need? - including the rules of thumb for vanilla, Paper and large modpacks. If the server starts but players cannot connect, continue with Fix connection errors.

Frequently asked questions