Why is My Minecraft so Laggy?

The Problem: Each mob runs AI calculations 20 times per second. Pathfinding alone can consume massive resources, especially when mobs can’t reach their target.

Immediate Fixes:

1. Set mob caps: Limit animals to 10-15 per pen
2. Kill excess mobs: /kill @e[type=cow,distance=..50,limit=30,sort=random]
3. Fix zombie AI loops: Ensure villagers are fully enclosed or 3+ blocks away
4. Use mob switches: Fill the mob cap to prevent new spawns
5. Name tag farms: Named mobs don’t despawn but still count toward caps

Long-term Solutions:

• Redesign farms: Use water streams to concentrate mobs in killing chambers
• Add activation rails: Keep minecarts with mobs stationary when not needed
• Install mob limiters: Plugins like MobLimiter or StackMob for servers
• Optimize villager setups: Minimize workstation scanning with proper placement

The Problem: Item frames cause severe FPS drops, especially with maps. Just 200 map-filled frames can crash servers.

Solutions:

1. Replace with alternatives:
   • Use signs for labeling
   • Armor stands for displays
   • Paintings for decoration
2. Optimize placement:
   • Never use maps in item frames for decoration
   • Space frames at least 2 blocks apart
   • Keep them out of spawn chunks
3. Technical fixes:
   • Install Entity Culling mod (hides unseen entities)
   • Use texture packs with simplified item models
   • Set entity distance to minimum in video settings

How block updates work: When redstone changes state, it notifies all adjacent blocks. They check if they need to update, potentially triggering more updates. A single redstone line powering off can cause thousands of updates.

Lag Severity by Component:

Optimization Techniques:

1. Minimize dust usage:
   • Use repeaters instead of long dust lines
   • Replace dust with rails + powered rails where possible
   • Use target blocks for wireless redstone
2. Control update frequency:
   • Add delays between operations
   • Use slower clocks (2-4 seconds vs 1 tick)
   • Batch operations instead of continuous processing
3. Localize contraptions:
   • Build machines in single chunks
   • Keep redstone below Y=0 to reduce light updates
   • Encase machines in solid blocks

The Problem: Redstone torches and lamps cause expensive lighting recalculations when they toggle. Before 1.8, even redstone dust caused light updates.

# Fill your redstone area with torches at max light
/fill ~-10 ~-1 ~-10 ~10 ~5 ~10 torch replace air

Best Practices:

• Avoid flashing lights: Don’t use redstone lamps for aesthetics
• Box in machines: Fully enclose redstone to prevent light spread
• Use daylight sensors: For timing, they don’t cause block updates
• Substitute components: Replace torches with repeaters where possible

Java vs Bedrock Differences:

The Cost: Generating a single chunk requires calculating terrain, caves, structures, decorations, and mob spawns. This can take 50-200ms per chunk. Flying with elytra can demand 20+ new chunks per second.

Pre-generation Solutions:

1. Chunky (recommended):
   Chunky Commands

   /chunky radius 5000
   /chunky world world
   /chunky start

2. WorldBorder method:
   WorldBorder Pre-gen

   /worldborder center 0 0
   /worldborder set 10000
   /wb world fill 1000
   /wb fill confirm

3. Benefits of pre-generation:
   • Eliminates exploration lag
   • Reduces disk I/O during gameplay
   • Allows finding all structures in advance
   • Stabilizes server performance

Warning: Pre-generation doesn’t reduce lag from chunk contents (entities, redstone). It only eliminates generation lag.

Optimization Strategy:

• Client render distance: Set to 8-12 for gameplay
• Server view-distance: Keep at 8 or lower
• Simulation-distance: 6-8 is optimal
• Paper/Spigot no-tick-view-distance: Can be higher (10-12)

view-distance=8
simulation-distance=6
entity-broadcast-range-percentage=75

Hidden Performance Killers:

• Biome Blend: At 15×15, checks 225 blocks per grass block!
• Clouds: Fancy clouds surprisingly expensive
• Vignette: Darkened screen edges cost 2-3 FPS
• View Bobbing: Causes extra calculations

The Goldilocks Principle: Too little RAM causes stutters, but too much triggers lengthy garbage collection pauses.

-XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 
-XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch 
-XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M 
-XX:G1ReservePercent=20 -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 
-XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 
-XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem 
-XX:MaxTenuringThreshold=1 -Dusing.aikars.flags=https://mcflags.emc.gs 
-Daikars.new.flags=true

Essential Configuration Changes:

max-entity-collisions: 2
optimize-explosions: true
mob-spawner-tick-rate: 2
container-update-tick-rate: 3
grass-spread-tick-rate: 4
armor-stands-tick: false
per-player-mob-spawns: true

merge-radius:
  item: 4.0
  exp: 6.0
entity-activation-range:
  animals: 16
  monsters: 24
  raiders: 32
  misc: 8

• ClearLagg: Removes ground items, limits mobs
• Farm Limiter: Prevents oversized farms
• Insights: Identifies lag sources in real-time
• Spark: Advanced performance profiler
• ChunkyGen: Pre-generates world chunks
• EntityTrackerFixer: Fixes ghost entities

1.14-1.16 Villager Lag:

• Keep villagers in 1×1 cells
• Destroy beds during day
• Use VillagerOptimizer plugin
• Limit to 30 villagers per area

1.21.5 Rendering Issues:

• Install ImmediatelyFast mod
• Downgrade to 1.21.4 if possible
• Disable shaders temporarily
• Wait for 1.21.6 fixes

General Version Advice:

• Most stable: 1.12.2, 1.16.5, 1.19.4
• Best modded: 1.12.2, 1.16.5, 1.20.1
• Best vanilla performance: 1.19.4, 1.20.1
• Avoid for servers: 1.14.x, 1.17.0, 1.21.5

Fabulously Optimized (Fabric):

• Includes Sodium, Lithium, Starlight, and more
• OptiFine parity with better performance
• Regular updates for new versions
• Available on CurseForge and Modrinth

Simply Optimized (Fabric):

• Minimal approach, pure performance
• No visual changes to vanilla
• Server-friendly optimizations

Manual Combination (Best Performance):

1. Sodium + Iris (shaders)
2. Lithium + Starlight/Moonrise
3. FerriteCore + Entity Culling
4. ModernFix + FastLoad
5. Memory Leak Fix + Debugify