Out of Memory (OOM) Crashes

An out-of-memory (OOM) crash happens when your server tries to use more RAM than it has allocated. The system kills the process to protect the node, and your server stops.

Recognizing an OOM Crash

OOM crashes can appear in different ways:

• The panel’s crash notice in the console says the server ran out of memory, or the server exits with code 137. The server went over its plan’s memory limit.
• Console shows “Killed”, “Out of memory”, or similar messages
• Java-based games log java.lang.OutOfMemoryError. Java ran out of room inside the memory set aside for the game, even when the crash notice doesn’t say the server ran out of memory.
• Server stops abruptly with no clear error

The crash notice is the surest sign. The Memory Usage graph alone can mislead on Java-based games like Minecraft, which sit near the limit even when nothing is wrong (see Reading the Memory Graph).

Crash notice doesn’t mention running out of memory, and the log has no OutOfMemoryError? The crash has a different cause. See Server Won’t Start or Keeps Crashing?

Common Causes

Too many mods or plugins. Every mod and plugin consumes RAM at startup and during operation. Complex mods that add entities, dimensions, or world generation use more than lightweight utility mods.

Large or complex worlds. Older worlds accumulate data over time. Pre-generated terrain, entity-heavy areas, and complex builds all increase memory usage when loaded.

High player count. Each player loads chunks around them and adds entities to track. More concurrent players means more RAM in use.

Memory leaks. Some mods or plugins don’t release memory properly over time. If your server runs fine initially but crashes after hours of uptime, scheduling a daily restart can help. See The Schedule Manager.

Insufficient RAM for the game. Some games and modpacks simply require more RAM than a given plan provides.

Diagnosing the Issue

Start by identifying when crashes occur:

• At startup: Likely not enough RAM for your mods/plugins to load, or the heap size needs adjustment
• During play: Triggered by player activity, chunk loading, or specific game events
• After extended uptime: Suggests a memory leak that accumulates over time

Reading the Memory Graph

The Memory Usage graph sits below the console (see Usage Graphs). Read it while the problem is happening:

• Near the limit all the time, even with nobody online: normal for Java-based games like Minecraft. Java holds on to the memory it’s given and frees it only when it needs the room. This isn’t a leak on its own.
• Climbs over hours, drops after a restart, and the problem comes back as it climbs: something is holding on to memory. A daily restart usually fixes this without a bigger plan.
• Well below the limit while players lag: memory isn’t the cause, and more RAM won’t help. See Server Lag or Not Enough RAM?

Adjusting Max Heap Size

Some games, including Minecraft and Hytale, have a heap setting in Server Options. On Minecraft it’s labeled Max Heap Size Percentage. It controls how much of your plan’s RAM goes to the game and how much is left for Java’s own overhead.

• The crash notice says the server ran out of memory, or shows exit code 137: the server went over your plan’s limit. Lower the percentage to leave more room for overhead, or reduce memory use with the tips below.
• The log shows java.lang.OutOfMemoryError while the Memory Usage graph stays well below the limit: the heap may be too restricted. Try increasing it.

To change it, open Server Options in the Game Control Panel sidebar, change one value at a time, and restart. Watch the Memory Usage graph before you change anything else. If your game doesn’t have this option, skip to the next section.

Minecraft: check your Java version first

How much overhead Java needs varies by Minecraft version and server software. Before you change Max Heap Size Percentage:

1. Check the Java Version in Server Options. It must match your Minecraft version. See Which version do I need?
2. Check the JVM Flags for that Java version. What belongs there depends on your Java version. See Aikar’s Flags before you add or change anything.
3. Recheck the percentage after a version or software change. A value that worked before an update may not leave enough overhead after it. See Startup Parameters.

Raising the percentage doesn’t add RAM to your plan. It moves RAM from Java’s overhead to the game, and Java needs that overhead to run.

Optimization Tips

Before upgrading RAM, try reducing memory usage:

• Remove unused mods and plugins. If you’re not using it, it’s still consuming RAM.
• Reduce view distance or simulation distance. Fewer loaded chunks means less memory. On Minecraft, see Server Optimization.

When to Upgrade RAM

If you’ve adjusted heap size, optimized your setup, and still hit OOM crashes, your server may need more RAM. This is common when:

• Your player count has grown beyond what your current plan supports
• You’ve added mods or plugins that require more resources
• You’re running a game or modpack with high baseline requirements

For Minecraft sizing, see How Much RAM Do I Need for a Minecraft Server? To change your plan, see Upgrade/Downgrade Your Service.

Still Not Working?

If your server still crashes out of memory, contact our support team with:

• Your Server UUID
• The crash log link from the crash notice, or from Upload logs beside the console
• Roughly when the crashes started
• What you’ve already changed (heap setting, JVM flags, mods, or plugins)