Quick answer: If your Minecraft server won’t start, the most common reasons are: the EULA isn’t accepted (eula.txt still says false), the wrong Java version, not enough RAM allocated, the port is already in use, or a corrupted world/config file. The server console log almost always tells you which one — read the last few lines.
A server that starts and immediately closes is frustrating, but the fix is usually quick. Work through these in order.
1. Accept the EULA
The single most common reason a fresh server won’t start: you have to agree to Mojang’s license. Open eula.txt in the server folder and change eula=false to eula=true, then save and restart. If the log says “You need to agree to the EULA,” this is it.
2. Wrong Java Version
Modern Minecraft needs a current Java (Java 21 for the latest releases). If the log shows UnsupportedClassVersionError or complains about the Java version, install the right one and confirm with java -version. Older Java can’t run newer server jars.
3. Not Enough RAM
If you see Could not reserve enough space or an out-of-memory error, you’ve either allocated more RAM than the machine has, or too little for a modpack. Adjust the -Xmx flag to a value your system can handle — see how to allocate RAM. Modded servers need much more than vanilla.
4. Port Already in Use
An error like Address already in use or FAILED TO BIND TO PORT means another program (often an old server instance that didn’t fully close) is holding port 25565. Close the other process, or change server-port in server.properties.
5. Corrupted World or Config
- If it crashes while loading a world, a corrupted chunk may be to blame — restore from a backup.
- A broken mod or plugin can crash startup. Remove recently added ones one at a time to find the culprit — the crash log names the failing mod.
- A typo in
server.properties(e.g. a bad value) can stop it booting — check anything you edited recently.
Always Read the Log
The server console (or logs/latest.log) prints the exact error before it closes. Scroll to the bottom and read the last stack trace — 90% of the time it names the problem directly (EULA, Java, memory, port, or a specific mod). Copy that line into a search if you’re unsure.
Tired of wrestling with Java, RAM flags, and crash logs? A hosted Minecraft server handles the environment for you — one-click server types, managed Java, and easy RAM sliders. See also how to make a server and can’t connect to server.
FAQ
Why does my server close right after starting?
Almost always the EULA isn’t accepted (set eula=true in eula.txt) or the Java version is wrong. Check the log’s last lines — it states the reason.
What does “failed to bind to port” mean?
Another process is already using port 25565 — usually a previous server instance that didn’t shut down. Close it, or change the port in server.properties.
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