# How to Fix 'Can't Keep Up' and Tick Loop Crashes on Your Minecraft Server (/docs/minecraft/fix-server-tick-loop) import { Step, Steps } from 'fumadocs-ui/components/steps'; **"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 [#symptoms] | Symptom | Severity | | -------------------------------------------------- | ----------------------------------------------- | | Occasional "Can't keep up" during world generation | Normal — ignore | | Constant "Can't keep up" during gameplay | Bad — fix the underlying lag | | TPS below 15 in `/spark tps` | Bad — players will feel it | | `Exception in server tick loop` crash | Critical — server died | | `Watchdog Thread/ERROR` in logs | Critical — single tick exceeded `max-tick-time` | Diagnose with Spark [#diagnose-with-spark] The fastest way to find what's causing tick lag is the **Spark** profiler. Install Spark [#install-spark] Drop the [Spark](https://spark.lucko.me/) JAR into your `plugins/` (Paper/Spigot) or `mods/` (Forge/Fabric) folder and restart. Full guide: [Setup Spark](/docs/minecraft/setup-spark). Check current TPS [#check-current-tps] In **Console** or in-game: ``` /spark tps ``` If TPS is below 18 sustained, you have a problem. Run a profiler [#run-a-profiler] ``` /spark profiler start ``` Wait 2–5 minutes during normal gameplay (or during the lag spike), then: ``` /spark profiler stop ``` Spark generates a web link. Open it. Read the report [#read-the-report] Look for the largest **self-time** entries. Common culprits: | What you see | Cause | | ------------------------------------ | -------------------------------------------- | | `ServerChunkCache.tick` / `ChunkMap` | Too many loaded chunks — lower view-distance | | `EntityType.tick` for one type | Mob farm — too many of that mob | | `LevelChunk.tickBlocks` | Heavy redstone or fluid ticks | | A specific plugin/mod class | That plugin/mod is the problem | | `GarbageCollector` | RAM pressure — increase RAM or fix leak | Common Causes and Fixes [#common-causes-and-fixes] Too Many Entities (Mob Farms) [#too-many-entities-mob-farms] Big mob farms with hundreds of mobs are the #1 lag source on most servers. **Fix:** * Install **[ClearLagg](https://www.spigotmc.org/resources/clearlagg.68271/)** to auto-clear ground items and entities * Install **[FarmControl](https://www.spigotmc.org/resources/farmcontrol.86923/)** to cap mob farms * Lower entity activation range in `spigot.yml`: ```yaml 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](/docs/minecraft/change-mob-spawn-rate). Chunk Generation Lag [#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](/docs/minecraft/pregenerate-chunks): ``` /chunky radius 5000 /chunky start ``` Run overnight before opening the server to players. Heavy Redstone [#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](/docs/minecraft/install-custom-jar) * Simplify or remove the worst offender (Spark will name the chunk) Bad Plugin or Mod [#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) [#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](/docs/minecraft/jvm-flags) * **Right-size** your RAM (see [How Much RAM](/docs/minecraft/how-much-ram)) — both too little and too much cause issues * Find memory leaks with `/spark heapdump` High View-Distance [#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](/docs/minecraft/render-distance). Stop Watchdog Crashes (Exception in server tick loop) [#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 [#temporary-workaround] Increase or disable the watchdog in `server.properties`: ```properties max-tick-time=120000 ``` Or to disable entirely (**not recommended**): ```properties 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 [#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 [#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 [#common-mistakes] | Mistake | Fix | | ------------------------------------ | ------------------------------------------------------ | | Increasing RAM as the first response | RAM rarely fixes tick lag — find the cause first | | Disabling the watchdog | Hides the problem, doesn't fix it | | Removing all plugins | The problem is usually one plugin — Spark will name it | | Ignoring "Can't keep up" warnings | They're a leading indicator of a future crash | | Restarting in a loop | Fix the cause — restarts won't help | Related Guides [#related-guides] * [Optimize Server](/docs/minecraft/optimize-server) * [Setup Spark](/docs/minecraft/setup-spark) * [Types of Server Lag](/docs/minecraft/types-of-server-lag) * [Pre-Generate Chunks](/docs/minecraft/pregenerate-chunks) * [JVM Flags](/docs/minecraft/jvm-flags) * [Render Distance](/docs/minecraft/render-distance) * [Mob Spawn Rate](/docs/minecraft/change-mob-spawn-rate)