Minecraft server keeps crashing: find the cause and stop it

While you look for the cause, players should not have to wait for you. Crash watch, on the Overview tab under Protection, restarts your server by itself when it crashes or stops responding. Leave it on.

Crash watch hides a crash from players, not from you. Every restart it makes is in the log, so the cause stays findable.

1. Open the Console tab and set the level filter to Errors.
2. Scroll to the last red block before the server stopped. The first line of that block names the kind of crash; the lines under it name the plugin or mod it happened in.
3. Did crash watch already restart the server? Then the log of the crash is in the Files tab, in the logs folder, and Minecraft also writes a full report to the crash-reports folder.

The Performance card on the Overview tab shows CPU, Memory and Players over the last 24 hours or 7 days. Open Memory and look at the moments your server crashed.

• It climbs to the top and the log says `OutOfMemoryError`: the server needs more memory than it has. Lower the view distance, remove plugins or mods you do not use, and pre-generate your world so new chunks do not pile up while players explore.
• It climbs slowly over days and never goes down after a restart: one plugin keeps too much in memory. Update your plugins first; memory leaks are usually fixed in a newer version.
• It stays well below the top: memory is not the problem. Go on to TPS.

Still at the top after that? How much RAM your server needs helps you pick the right size.

A Minecraft server runs 20 ticks per second. When it cannot keep up, it falls behind, and if one tick takes far too long the server gives up and stops. The Server health card in the Console tab shows it live.

• Falling behind only when many players are on, or in one place: look for big mob farms, lots of dropped items or huge redstone machines there.
• Falling behind all the time: measure it. Reduce lag on your server shows how spark tells you exactly what takes the time.
• Falling behind right after startup and then fine: that is normal while the world loads.

When the log names a plugin, check that plugin first. Crashes after a Minecraft update are very often a plugin that was made for the version before.

1. Open the Plugins tab. The Updates box at the top lists plugins with a newer version.
2. Update the plugin from the log, then restart the server.
3. No update, and it keeps crashing? Click Remove on it under Installed on this server, restart, and play for a while to be sure the crashes stop.

On a modded server the same goes for mods: the crash report names the mod. Update it, or remove it from the mods folder, and remember that players must then remove it too.

Does the server crash every time a player goes to one spot, or opens one chest? Then one chunk or one block entity is damaged, or a machine there overloads the server.

• Keep players away from that spot for now, for example by asking them or with a teleport.
• Look at the coordinates in the crash report. They point at the chunk.
• Restore a backup from before the problem began if the damage is big. Back up and restore your server shows how.

A crash report in the crash-reports folder looks long, but only a few lines matter. Near the top, the line Description names the kind of crash. Further down, a part called Affected level often says where in the world it happened.

To remove a broken entity, run this in the console with the coordinates from the report. It removes everything except players within two blocks of that spot:

execute positioned 120 64 -340 run kill @e[type=!minecraft:player,distance=..2]

For a broken block, setblock 120 64 -340 minecraft:air with its coordinates removes it, together with whatever it held. Make a backup first. Paper catches many of these crashes itself: it removes the failing entity and writes Entity threw exception at with the spot in the log instead of crashing.

Write down the time of each crash for a few days, from the log or from the Discord notifications of crash watch. The pattern usually points straight at the cause.

A daily restart keeps a slow memory leak from ever reaching the top while you wait for a fixed version. Schedule automatic restarts sets it up with a warning for players.

Change one thing at a time and then let the server run as players normally use it. If you change three things at once and the crashes stop, you do not know which one fixed it. Save the world before each test by typing save-all in the console, or use the button for it under Quick commands.

Still crashing and you do not know why? Send us a message from the client area with the time of the crash. We read the log with you.

• Make a backup before every change, so a bad update costs minutes instead of a world.
• Update plugins and mods one at a time, with a restart and a short test in between.
• Keep some memory free at the busiest hour; a graph that touches the top every evening is a crash waiting to happen.
• Pre-generate the world inside a border, so exploring never pushes the server over the edge.
• Read the console after each restart for new warnings, before players find the problem for you.