Minecraft server won't start: console errors and fixes

Minecraft server won't start? Read the console, match the error, and fix it in minutes. Triage for Java OOM, port collisions, mod crashes, and Bedrock.

Step 1: read the console

When a Minecraft server won't start, the answer is almost always in the console. Open Dashboard → your server → Console panel and scroll to the last 40 lines. The crash reason is usually a single line near the bottom. Match it against the patterns below before you do anything else.

Common Java errors and what they mean

java.lang.OutOfMemoryError

The JVM ran out of heap. Either the pack genuinely needs more RAM, or a runaway mod is leaking memory.

  • First, restart once. A single OOM after hours of uptime can be transient.
  • If it crashes again on boot, you're under-allocated. Trim mods you don't use, or upgrade to the next Java tier (Modded 6 GB, Heavy 10 GB, Extreme 14 GB).
  • For ATM family and RLCraft, Heavy 10 GB is the floor; don't try to run them on Modded 6 GB.

BindException: Address already in use

A previous server process is still holding the port, usually after an unclean crash. Click Restart once. The container recycles and the port frees. If it repeats on every boot, open a ticket so we can clear it node-side.

Could not reserve enough space for object heap

Looks scary, almost always the same root cause as OOM. Restart first. If it keeps happening, upgrade your tier. This one in particular often shows up when a modpack's -Xmx setting drifts above what the plan can give it.

Mod load failures

Lines like Failed to create mod instance, Mod ... requires ..., or a stack trace naming a specific mod ID. The fix is almost always:

  1. Note the mod name from the error.
  2. Open Files → /data/mods.
  3. Delete or rename the offending .jar to .jar.disabled.
  4. Restart.

Common triggers: a Forge mod dropped into a Fabric pack (or vice versa), a mod built for 1.20.1 on a 1.20.4 server, or a dependency mod missing. Check the mod's CurseForge or Modrinth page for the right loader and version.

Common Bedrock errors

Bedrock is quieter in the console but still tells you what went wrong:

  • Level requires a newer version or version mismatch: your world was last opened on a newer Bedrock client than the server. Update the server version in Settings → Version, or restore a backup from before the upgrade.
  • Addon conflicts: behaviour or resource pack errors print on boot. Remove the most recently added pack via Files → /data/worlds/<world>/behavior_packs (or resource_packs) and restart.
  • Allowlist (allowlist.json) parse errors: a stray comma or missing bracket. Open the file in Files and validate.

Step 2: the console is empty

If you hit Start and nothing prints at all, the container failed before Minecraft itself could run. Hit Stop, wait five seconds, then Start again. That recreates the container from scratch and usually clears the wedge. If it still won't start with an empty console, open a ticket from Dashboard → Support; we'll check the node-level logs.

Step 3: did you just install a mod or plugin?

If the last thing you did before the crash was install or update an addon, that's almost certainly it.

  1. Open Files.
  2. Go to /data/mods (Forge, Fabric, NeoForge) or /data/plugins (Paper, Spigot, Purpur).
  3. Move the suspect file out, or rename to .disabled.
  4. Restart.

If that fixes it, check the addon's page for version compatibility before putting it back.

Playing a different game?

These errors are Minecraft-specific (Java and Bedrock). Other games crash in their own ways:

If your Minecraft server boots but feels sluggish once players join, that's a different problem: see Fixing Minecraft server lag.

Last updated 2026-05-20. Notice a mistake? Tell us.

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