How do I analyze a Minecraft crash log?

Upload your latest.log, debug.log or crash report into MCDoctor. The AI automatically detects issues, errors, exceptions, mod conflicts and gives a clear explanation and fix.

Does MCDoctor support Paper, Purpur, Fabric, Spigot, or Forge logs?

Yes. MCDoctor supports all major Minecraft server types including Paper, Purpur, Spigot, Bukkit, Fabric, Quilt, Forge, NeoForge, and Vanilla.

Can MCDoctor fix mod or plugin compatibility issues?

Yes. MCDoctor identifies mod/plugin conflicts, outdated versions, loading failures, missing dependencies, and configuration errors.

Is MCDoctor safe to use?

MCDoctor only analyzes your log file, and your data is not shared, sold, or stored beyond the technical diagnostic process.

Why is my Minecraft server crashing?

Crashes usually come from mod/plugin conflicts, invalid configurations, insufficient RAM, corrupted worlds, bad datapacks, or outdated server software. MCDoctor identifies the exact cause automatically.

Does MCDoctor detect Java issues?

Yes. MCDoctor detects wrong Java versions, JVM argument errors, memory issues, and corrupted installations.

What files can I upload?

You can upload latest.log, debug.log, crash-reports, Paper logs, Fabric logs, server crash stacks, and Modloader errors.

Is the analysis instant?

Yes. MCDoctor provides instant AI-powered analysis, usually in under two seconds.

Common Server Issues – Full Error Encyclopedia

Server Stuck on Loading

Preparing spawn area: 0%

The world can’t generate properly due to CPU overload, corrupt chunks or heavy worldgen.

Fix: Reduce worldgen load, repair corrupt chunks (MCA Selector), or allocate more CPU/RAM.

Failed to Bind to Port

Address already in use

Another server instance is already using the same port. Stop all Java processes or change the port.

Fix: Kill other Java instances or change the server port in server.properties.

Unsupported Java Version

Unsupported major.minor version

Your server is running the wrong Java version. Match Minecraft to the required Java version.

Fix: Install and run the correct Java version for your Minecraft server.

Missing Mod / Dependency

Mod X requires Mod Y

A required dependency is missing. Install the mod version specified in the crash log.

Fix: Install all required dependencies exactly as listed in the crash log.

Mismatched Mod Versions

Received invalid mod channel

Client and server don’t share the same mod versions. Sync your modpack.

Fix: Ensure client and server share identical mod versions.

Can't Keep Up!

Server overloaded

TPS drops caused by entity overload, worldgen or weak CPU. Optimize chunks or switch to Paper.

Fix: Reduce entities, limit worldgen, or install Paper for performance improvements.

Ticking Entity

Ticking entity crash

An entity has corrupted NBT data. Remove the entity with a region editor.

Fix: Delete or repair the corrupted entity using MCA Selector.

Invalid Session

Invalid session token

Authentication expired. Log out and log back into the official Minecraft launcher.

Fix: Logout/login in the Mojang/Microsoft launcher to refresh the session.

Resource Pack Error

Invalid pack.mcmeta

JSON formatting error in the resource pack. Validate and fix syntax.

Fix: Correct the JSON structure inside pack.mcmeta using a validator.

World Corruption

level.dat corrupted

The main world file is damaged. Restore from backup or use level.dat_old.

Fix: Restore level.dat from level.dat_old or from a backup.

Out of Memory

Java heap space

The server ran out of RAM during world generation or heavy tasks. Increase Xmx or reduce loaded chunks.

Fix: Increase the RAM (Xmx) or reduce render/simulation distance.

Invalid or Corrupt JAR

Error: Invalid or corrupt jarfile

The server JAR is damaged or incomplete. Re-upload a clean server.jar.

Fix: Upload a fresh, intact server.jar and ensure the download wasn’t corrupted.

Datapack Load Failure

Failed to load datapack

A datapack contains invalid JSON or unsupported features. Disable datapacks from world folder.

Fix: Remove or repair the broken datapack by validating its JSON files.

Coremod Crash (Forge)

java.lang.ClassCastException

A coremod injects invalid bytecode. Remove outdated mods or update Forge.

Fix: Remove outdated coremods or update Forge to a supported version.

Plugin Conflict

java.lang.NoSuchMethodError

Two plugins use incompatible API versions. Update or remove old Bukkit/Spigot plugins.

Fix: Update or remove conflicting plugins using outdated API methods.

Fabric Loader Crash

Error while applying mixin

A Fabric mod injects into an unsupported class. Happens with version mismatches.

Fix: Update Fabric Loader and mods so all versions are compatible.

NeoForge Crash

Mod X attempted to load class Y improperly

Newer NeoForge builds break older mods. Check compatibility tables before installing.

Fix: Install the proper NeoForge version required by all installed mods.

Corrupted Plugin Config

SnakeYAML parse error

A plugin config.yml contains invalid indentation. Reformat YAML correctly.

Fix: Correct YAML indentation or regenerate the config from default files.

Massive Entity Lag

Entity count over 15,000

Farms or mob caps exceed limits. Use /kill @e[type=!player] with caution or reduce mob farms.

Fix: Reduce mob farms or manually remove excessive entities.

Redstone Lag

Excessive tile ticks

Heavy redstone clocks cause TPS drops. Replace clocks with observers or daylight sensors.

Fix: Replace laggy redstone clocks with observer-based or daylight alternatives.

Chunk Load Storm

High chunk load event rate

Players exploring new terrain cause CPU spikes. Pre-generate chunks or limit render distance.

Fix: Pre-generate chunks or lower server view distance.

Too Many Hoppers

Hopper tick overload

Large hopper arrays constantly check inventories. Replace with water streams or storage mods.

Fix: Replace hopper chains with water streams or efficient item transport systems.

Timed Out

Timed out

The client cannot keep up with the server. Caused by bad routing or overloaded CPU.

Fix: Check network routing, reduce server load, and increase CPU resources if needed.

Internal Exception

java.io.IOException: An existing connection was forcibly closed

Often caused by antivirus, firewall, or packet loss. Check network stability.

Fix: Disable interfering firewalls, antivirus, or resolve packet loss issues.

Server Not Showing in List

Can't resolve hostname

DNS isn’t propagating or SRV record is broken. Verify DNS configuration.

Fix: Correct your DNS A/SRV records and wait for DNS propagation.

Whitelist Error

You are not whitelisted

Player UUID changed or offline-mode is enabled. Add the correct username or UUID.

Fix: Add the player’s correct UUID to whitelist.json.

Corrupted Chunk

Chunk is already taken by another thread

A chunk is partially written. Use MCA Selector to remove or repair the region.

Fix: Open the region in MCA Selector and delete or repair the broken chunk.

Heightmap Error

Invalid heightmap

Custom worldgen or mods saved invalid heightdata. Regenerate the chunk.

Fix: Regenerate the affected chunk or remove faulty custom worldgen/datapacks.

Player Data Corruption

Failed to load playerdata

Player data is unreadable. Replace with backup or delete player .dat to reset.

Fix: Delete the corrupt player .dat file or restore it from a backup.

Structure Save Failure

Could not load structure pool

A datapack or mod overwrote structure templates incorrectly.

Fix: Remove or fix the datapack containing corrupted structure templates.

Invalid Shader

Unsupported shader pipeline

Shaders require OptiFine or Iris version matching your MC version.

Fix: Install the correct OptiFine or Iris version that matches your Minecraft version.

Texture Missing

pink/black checkerboard

The texture files are missing or incorrectly named. Check paths and pack.mcmeta format.

Fix: Verify all texture paths and ensure every referenced PNG exists and is properly named.

Sound Not Playing

Missing sound event

Resource packs with custom sounds require correct registry keys in sounds.json.

Fix: Check sounds.json and ensure all sound events are correctly registered.

High VRAM Usage

Out of video memory

High resolution (512x+) packs overload GPU memory. Use 128x or 256x textures.

Fix: Reduce texture resolution to 128x or 256x to fit GPU memory limits.

Ticking Block Entity (Furnace)

Ticking block entity: furnace

A furnace has corrupted NBT data. Remove or replace the block using MCA Selector.

Fix: Delete or replace the furnace block in MCA Selector to remove bad NBT.

Ticking Block Entity (Chest)

Ticking block entity: chest

A chest contains broken NBT data. Remove the chest from the region file.

Fix: Remove or replace the corrupted chest block using MCA Selector.

Watchdog Crash

A single server tick took 60.00 seconds

The server froze and the watchdog killed it. Common cause: infinite loops or heavy lag spikes.

Fix: Identify infinite loops or heavy tick tasks; optimize plugins, mods, or redstone.

Java Runtime Error

JNI error / Java exception

The Java installation is broken. Reinstall or switch to a stable distribution like Temurin.

Fix: Reinstall Java or switch to a recommended JDK such as Temurin.

Paper API Mismatch

Unsupported API version

A plugin was built for an older or newer Paper API. Update the plugin.

Fix: Install a version of the plugin matching your Paper API version.

Forge Version Incompatible

Requires Forge X.Y.Z

The mod requires a more recent Forge version than the one installed.

Fix: Install the required Forge version listed by the mod."

Fabric API Missing

Fabric API not found

Many Fabric mods require Fabric API. Add it to the mods folder.

Fix: Download and add Fabric API to the server’s mods folder.

NeoForge Library Missing

Missing required library

A required library mod is missing. Install all dependencies.

Fix: Install all libraries listed as dependencies for the mod.

Duplicate Mod

Found duplicate mod

Two versions of the same mod are present. Remove duplicates.

Fix: Delete all duplicate mod JARs and keep only one version.

Broken Plugin

Invalid plugin.yml

The plugin.yml file is malformed. Re-download the plugin.

Fix: Re-download a clean, valid version of the plugin.

Connection Reset

Connection reset by peer

Network instability or firewall interference caused the connection to end abruptly.

Fix: Check network stability, firewall rules, and router configuration.

UUID Conflict

UUID already in use

Player data conflicts between offline-mode and online-mode. Clear duplicate UUID files.

Fix: Delete duplicate UUID playerdata files and ensure the server runs in the correct mode (offline/online).

Missing Main Class

Could not find main class

The server JAR is incomplete or incorrectly built. Use an official server .jar.

Fix: Replace the broken JAR with the official Minecraft or modded server JAR.

Invalid Gamerule

Invalid gamerule value

A gamerule was set to an invalid type. Reset using /gamerule valid values.

Fix: Reset the gamerule to a valid numerical or boolean value.

World Border Bug

Invalid world border

The world border file is corrupted. Reset the world border settings.

Fix: Reset world border using /worldborder commands or delete the corrupted border file.

Villager Data Crash

Error loading villager

A villager has corrupted NBT data. Remove the villager from the region file.

Fix: Open the region in MCA Selector and delete the corrupted villager entity.

Advancement Corruption

Failed to load advancement

An advancement JSON is invalid or corrupted. Remove the broken file.

Fix: Delete the corrupted advancement JSON from the world folder.

Scoreboard Overflow

Scoreboard too large

The scoreboard file has grown too large. Reset scoreboard.dat.

Fix: Delete scoreboard.dat to regenerate a clean scoreboard.

Invalid Biome Source

Failed to load biome

Custom biome data is corrupted. Remove problematic datapacks.

Fix: Remove or repair the datapack providing custom biome definitions.

Java Native Crash

EXCEPTION_ACCESS_VIOLATION

Caused by outdated GPU drivers or Java native bugs. Update GPU drivers.

Fix: Update your GPU drivers and ensure Java is updated to a stable version.

Corrupted Map Item

Error loading map

A map item contains corrupted NBT data. Delete the map item from playerdata.

Fix: Remove the corrupted map from playerdata or inventory files manually.

Missing Dimension

Dimension type not found

A custom dimension failed to load. Remove broken datapack dimensions.

Fix: Remove broken custom dimension JSON files or datapacks.

Wrong Mod Loader

ModLoader mismatch

A Fabric mod is on Forge, or vice versa. Use the correct loader.

Fix: Install the mod version corresponding to your loader (Fabric, Forge, NeoForge).

Plugin Event Crash

Event handler exception

A plugin error occurred during an event. Update or remove the plugin.

Fix: Update or replace the plugin causing the faulty event handler.

Missing Region File

Region file missing

A region file was deleted or corrupted. Restore from backup.

Fix: Restore missing region files from backup or recreate the world region.

Thrown Entity Crash

Error ticking projectile

A projectile entity (arrow, snowball, etc.) has corrupted data.

Fix: Delete the corrupted projectile entity using MCA Selector.

AI Pathfinding Lag

Excessive pathfinding

Too many mobs calculating paths. Reduce mob counts.

Fix: Reduce mob population in the affected area to decrease pathfinding load.

Broken Beacon

Invalid beacon data

A beacon block has corrupted NBT. Remove and rebuild.

Fix: Break and rebuild the beacon to regenerate clean NBT data.

Hopper Loop

Infinite item loop

Hoppers are transferring items in a loop. Break the loop.

Fix: Break or redesign the hopper circuit to eliminate circular item transfers.

Custom Model Data Crash

Invalid custom model

Incorrect model references in the resource pack. Fix JSON model paths.

Fix: Correct the model path references in the resource pack’s JSON files.

Java GC Lag

High garbage collection

JVM is spending too much time cleaning memory. Reduce allocation or increase RAM.

Fix: Increase RAM or lower memory allocation spikes to reduce GC pressure.

Mobcap Exceeded

Too many mobs spawning

Reduce mob farms or lower simulation distance.

Fix: Reduce mob spawners, limit farm designs, or lower simulation distance.

Outdated Bukkit Version

Unsupported server version

The plugin does not support the server version. Update Bukkit/Spigot.

Fix: Update your server to a newer Spigot/Bukkit/Paper version.

Missing ProtocolLib

Dependency not found

Many plugins require ProtocolLib. Install it on your server.

Fix: Install ProtocolLib in the plugins folder.

Infinite Tick Loop

Tick loop detected

A plugin or mod is causing infinite recursion. Remove problematic code.

Fix: Identify and remove the plugin or mod causing infinite tick recursion.

Packet Flood

Received too many packets

Too many packets were sent too quickly. Could be a bot or modded client.

Fix: Enable anti-bot protection or rate-limit packets using plugins or firewall rules.

Ghost Player

Player already logged in

The server thinks the player is still online. Restart the server or wait for timeout.

Fix: Restart the server or delete the player's UUID/entry from the online players list.

Incomplete Startup

Server failed to start

A plugin or mod crashed early during initialization.

Fix: Remove the faulty plugin or mod and check logs for the specific cause.

World Save Failure

java.io.IOException: No space left on device

The server cannot write world data because the storage device is full or the folder has restricted permissions.

Fix: Free disk space or correct file permissions on the server directory.

Client Mod Installed on Server