What is Pre-generation in Minecraft? All You Need to Know.

Pre-generation is the process of generating chunks in advance before players explore them, reducing lag caused by real-time chunk generation. Instead of your server scrambling to create terrain on-demand as players venture into new areas, pre-generation handles all the heavy lifting during downtime, creating a smooth, lag-free exploration experience when your server opens to players.

It's one of the most effective performance optimizations available for Minecraft servers.​

Why Pre-generate Chunks?

Eliminates Exploration Lag

Real-time chunk generation causes noticeable lag spikes:​

• TPS drops from 20 to as low as 2-8 when multiple players explore simultaneously​
• Block break delays of 3+ seconds while chunks generate nearby​
• Stuttering and freezes when flying or traveling quickly​
• Chunk loading errors where terrain appears slowly or incompletely​

With pre-generation, chunks already exist and players explore smoothly without performance dips.​

Consistent Server Performance

Pre-generated worlds maintain stable CPU usage:​

• No unpredictable CPU spikes during exploration​
• Consistent TPS of 20 even with multiple players exploring different areas​
• Better resource allocation for gameplay mechanics instead of chunk generation​

One server admin reported going from constant TPS drops (14-8 TPS) to perfect 20 TPS stability after pre-generating their world​

Works with World Borders

Pre-generation pairs perfectly with world borders:​

1. Set a world border to define your play area
2. Pre-generate all chunks inside that border
3. Players can explore freely within the border without generating new chunks

This combination prevents infinite world growth while ensuring smooth performance.​

Ideal for Custom World Generation

Servers using custom terrain generators (like Terra, Epic World Generator) require pre-generation for playable performance​

• Custom generation is significantly more CPU-intensive than vanilla terrain
• Real-time custom generation causes severe lag even for single players
• Pre-generation makes custom worlds viable for multiplayer

How Long Does Pre-generation Take?

Pre-generation time depends on radius, the amount of vCores your server has, and storage type:​

Performance During Pre-generation

While Chunky runs, expect server performance to be impacted:

• High CPU usage (often 80-100% on one core)​
• Increased RAM consumption for holding generated chunks​
• Potential TPS drops if generation speed is set too high​

Always run pre-generation before opening your server to players, never during active gameplay.​

Pre-generation Settings and Optimization

Generation Speed

Control how many chunks Chunky generates per second:

/chunky speed hunks-per-second>

Recommended speeds:

• 1-2 chunks/sec: Safe for servers with active players (minimal TPS impact)
• 5-10 chunks/sec: Good balance for offline pre-generation
• 20+ chunks/sec: Fast generation but may cause lag​

Shape Selection

Chunky can pre-generate in different shapes:​

• square (default): Pre-generates a square area
• circle: Pre-generates a circular area (more natural border)
• rectangle: Pre-generates a custom rectangular region

/chunky shape circle

Common Pre-generation Issues

"Server lags after pre-generation finished"

Possible causes:

• Too many loaded chunks: Pre-generated chunks stay loaded in memory initially​
• Solution: Restart your server to unload chunks and clear cache​

"Pre-generation is extremely slow"

Causes and fixes:

• Using HDD instead of SSD: Upgrade to SSD/NVMe for 10x+ faster generation​
• Low chunk speed setting: Increase with /chunky speed​
• Heavily modded generation: Custom terrain mods slow generation significantly. The key is to be patient​

"TPS tanks to 2-3 during generation"

This is somewhat normal for intensive generation. Solutions:​

• Lower the generation speed with /chunky speed 5​
• Pre-generate during server downtime when no players are online​
• Allocate more RAM to your server (8GB+ for modded servers)

When to Pre-generate

Pre-generation is most valuable when:

• Opening a new server: Pre-generate before your grand opening​
• Before major updates: Pre-generate to avoid real-time lag during launch rush​
• Using custom terrain generators: Essential for playable performance​
• Running modded servers: Modded generation is far more intensive than vanilla​

When NOT to Pre-generate

You might skip pre-generation if:

• Your server has unlimited exploration and you want infinite world growth​
• You have abundant CPU resources and low player counts​
• You're running a creative-only server with minimal exploration​

However, even these scenarios benefit from partial pre-generation around spawn.​