How to Fix 'Can't Keep Up' and Tick Loop Crashes on Your Minecraft Server

"Can't keep up! Is the server overloaded?" means your server is falling behind on game ticks (Minecraft runs 20 ticks per second; missing this target = lag). When the lag is severe enough — or a single tick takes longer than max-tick-time (60 seconds by default) — the watchdog kills the server with an "Exception in server tick loop" crash.

This guide covers both the warning and the crash. The fix process is the same: find what's eating tick time, then reduce it.

Symptoms

Diagnose with Spark

The fastest way to find what's causing tick lag is the Spark profiler.

/spark tps

/spark profiler start

/spark profiler stop

Common Causes and Fixes

Too Many Entities (Mob Farms)

Big mob farms with hundreds of mobs are the #1 lag source on most servers.

Fix:

• Install ClearLagg to auto-clear ground items and entities
• Install FarmControl to cap mob farms
• Lower entity activation range in spigot.yml:

entity-activation-range:
  animals: 16
  monsters: 24
  misc: 8

• Reduce mob-spawn-range in spigot.yml from 8 to 6
• Set per-chunk entity caps in paper-world-defaults.yml

See Mob Spawn Rate.

Chunk Generation Lag

When players explore new areas, the server generates new chunks — which is the most CPU-intensive thing Minecraft does.

Fix: Pre-generate the world with Chunky:

/chunky radius 5000
/chunky start

Run overnight before opening the server to players.

Heavy Redstone

Large redstone machines (item sorters, factory contraptions, music boxes) can eat 50% of a tick on their own.

Fix:

• Use Paper's redstone optimizer (config/paper-world-defaults.yml → redstone-implementation: ALTERNATE_CURRENT)
• Switch to a redstone-optimized JAR like Purpur
• Simplify or remove the worst offender (Spark will name the chunk)

Bad Plugin or Mod

A single broken plugin or mod can tank an entire server.

Fix: Read the Spark profiler — it names the plugin/mod by package. Update or remove it.

Insufficient RAM (GC Pauses)

If GC pauses are eating tick time, you'll see GarbageCollector near the top of Spark.

Fix:

• Apply Aikar's Flags
• Right-size your RAM (see How Much RAM) — both too little and too much cause issues
• Find memory leaks with /spark heapdump

High View-Distance

View-distance has a quadratic effect on chunk count and a linear effect on per-tick work.

Fix: Lower view-distance to 6–8 and simulation-distance to 4–6 in server.properties. See Render Distance.

Stop Watchdog Crashes (Exception in server tick loop)

When a single tick exceeds max-tick-time (default 60000 ms = 60 seconds), the watchdog kills the server.

Temporary workaround

Increase or disable the watchdog in server.properties:

max-tick-time=120000

Or to disable entirely (not recommended):

max-tick-time=-1

Warning: Raising max-tick-time doesn't fix the lag — it just hides the symptom. Use it as a temporary measure while you find the real cause with Spark.

Real fix

Find the operation that took 60+ seconds in Console at the time of the crash. The watchdog logs a thread dump showing exactly what was running. Common culprits:

• A plugin loop with no exit condition
• A worldedit operation on millions of blocks
• A mod doing synchronous I/O on the main thread
• A broken pathfinding loop on a huge mob

Quick Wins Checklist

1. ✅ Lower view-distance to 8, simulation-distance to 6
2. ✅ Apply Aikar's Flags
3. ✅ Pre-generate chunks with Chunky
4. ✅ Install Spark and identify the top offender
5. ✅ Switch to Paper if not already
6. ✅ Install ClearLagg + FarmControl

Most servers see a 2–3× TPS improvement from these alone.

Common Mistakes

Related Guides

• Optimize Server
• Setup Spark
• Types of Server Lag
• Pre-Generate Chunks
• JVM Flags
• Render Distance
• Mob Spawn Rate