# How to Fix a Minecraft Server That Won't Start (/docs/minecraft/fix-server-wont-start) import { Step, Steps } from 'fumadocs-ui/components/steps'; When a Minecraft server refuses to start, the **first error in the Console** almost always tells you exactly what's wrong. Most startup failures fall into one of seven categories: EULA, Java version, RAM, mods/plugins, corrupted JAR, world corruption, or port conflict. > **The golden rule of Minecraft troubleshooting:** Read the *first* error in the Console, not the last. Later errors are usually side effects of the first. Diagnostic Flow [#diagnostic-flow] Open Console and read the first error [#open-console-and-read-the-first-error] In the [XGamingServer Panel](https://panel.xgamingserver.com), open **Console**. Scroll to the start of the latest startup attempt. Look for the **first** line containing `ERROR`, `Exception`, `FATAL`, or `Failed`. Match the error to the table below [#match-the-error-to-the-table-below] Use this table to identify the cause and jump to the fix. Errors and Fixes [#errors-and-fixes] You need to agree to the EULA [#you-need-to-agree-to-the-eula] Minecraft requires you to accept Mojang's EULA before the server runs. **Fix:** Open **Files**, edit `eula.txt`, change `eula=false` to `eula=true`, save, and restart. See [Accept the EULA](/docs/minecraft/agree-to-eula). UnsupportedClassVersionError or has been compiled by a more recent version of the Java Runtime [#unsupportedclassversionerror-or-has-been-compiled-by-a-more-recent-version-of-the-java-runtime] Your server JAR was built for a newer Java than the one running it. | Minecraft version | Required Java | | ----------------- | ------------- | | 1.20.5 and newer | Java 21+ | | 1.18 – 1.20.4 | Java 17+ | | 1.17 | Java 16+ | | 1.13 – 1.16 | Java 8 or 11 | | 1.12 and older | Java 8 | **Fix:** Open **Startup** in the panel and select the matching Java version (or Docker image). See [Java Version](/docs/minecraft/java-version). OutOfMemoryError / Java heap space / Exit code 137 [#outofmemoryerror--java-heap-space--exit-code-137] The server ran out of allocated RAM. **Fix:** Open **Startup** and increase memory. See [How Much RAM](/docs/minecraft/how-much-ram). Also check for memory leaks: a 4GB server hitting OOM with 5 players probably has a runaway entity or chunk loader. See [Optimize Server](/docs/minecraft/optimize-server). Address already in use [#address-already-in-use] Another process is using the port. **Fix:** Rare on hosted servers. Restart the server from the Dashboard. If it persists, contact support — the previous process may not have released the port. Crash on plugin or mod load (NoClassDefFoundError, ClassCastException, NoSuchMethodError) [#crash-on-plugin-or-mod-load-noclassdeffounderror-classcastexception-nosuchmethoderror] A plugin or mod is incompatible with your Minecraft version, your server software, or another mod. **Fix:** The error trace usually names the offending plugin/mod. Remove the most recently added file from `plugins/` or `mods/` and try starting again. See [Find / Read Crash Reports](/docs/minecraft/find-read-crash-reports). Session lock / level.dat is missing / chunk loading failed [#session-lock--leveldat-is-missing--chunk-loading-failed] World file corruption — usually from an unclean shutdown. **Fix options (in order):** 1. Delete `world/session.lock` (safe — it's a lock file, gets recreated) 2. Restore from **Backups** in the panel 3. Replace `level.dat` with `level.dat_old` from the world folder 4. Use an offline world editor (NBTExplorer) to inspect See [Fix: Session Lock](/docs/minecraft/fix-session-lock). Failed to start the minecraft server / Exit code 1 with no obvious error [#failed-to-start-the-minecraft-server--exit-code-1-with-no-obvious-error] The JAR may be corrupted or incomplete. **Fix:** From the panel **Settings**, click **Reinstall Server**. This re-downloads the server JAR. Your world and configs are preserved. Exception in server tick loop [#exception-in-server-tick-loop] The server started, then crashed during the first tick. Usually a bad world chunk, bad NBT data, or a broken plugin. **Fix:** See [Fix: Server Tick Loop](/docs/minecraft/fix-server-tick-loop). Java Exit Codes [#java-exit-codes] | Exit code | Meaning | | --------- | ------------------------------------------------ | | `0` | Clean shutdown | | `1` | General error — read the Console | | `137` | Out of memory (OOM kill) — increase RAM | | `139` | Segfault — usually JNI/native lib bug | | `143` | Server received SIGTERM (manual stop or timeout) | Full reference: [Java Exit Codes](/docs/minecraft/fix-java-exit-codes). Diagnostic Checklist [#diagnostic-checklist] Run through this in order — each step rules out one common cause: 1. ✅ **EULA** accepted? (`eula.txt` → `eula=true`) 2. ✅ **Java version** matches Minecraft version? (Startup tab) 3. ✅ **RAM** sufficient? (no exit 137 in history) 4. ✅ **No new mods/plugins** added since last working start? (remove and retry) 5. ✅ **JAR not corrupted**? (Reinstall Server) 6. ✅ **World not corrupted**? (delete session.lock, restore backup) 7. ✅ **Console first error read**? (not just the last line) If all 7 pass and the server still won't start, open a support ticket with the **full Console log** from the failed attempt. Common Mistakes [#common-mistakes] | Mistake | Fix | | -------------------------------------------- | ------------------------------------------------------ | | Reading only the last error | Read the **first** error — later ones are side effects | | Reinstalling the server (loses configs) | Reinstall is safe — keeps world and configs by default | | Deleting `world/` to "fix" startup | Almost never the problem — and you lose everything | | Ignoring the Java version warning | Wrong Java is the #2 cause of startup failures | | Restarting in a loop without reading Console | Each crash leaves the same error — read it once | Related Guides [#related-guides] * [Find / Read Crash Reports](/docs/minecraft/find-read-crash-reports) * [Java Exit Codes](/docs/minecraft/fix-java-exit-codes) * [Java Version](/docs/minecraft/java-version) * [How Much RAM](/docs/minecraft/how-much-ram) * [Accept the EULA](/docs/minecraft/agree-to-eula) * [Server Tick Loop](/docs/minecraft/fix-server-tick-loop) * [Session Lock](/docs/minecraft/fix-session-lock) * [Common Issues](/docs/minecraft/common-issues)