Pre-Generating Your Minecraft World

Why Chunk Generation Causes Lag

World generation is expensive because it assembles everything at once: biomes, terrain, structures, then per-block lighting. Vanilla does this on the server thread; Paper spreads parts across worker threads, but the final assembly still lands back on the main loop. When players push the frontier in different directions, the generation queue backs up and every loaded chunk waits on it, which players see as rubber-banding and frozen mobs.

• Spikes are worst on fresh spawns, border expansion, and after terrain-changing updates.
• Generated chunks load straight from disk, so player-triggered generation drops to zero.
• Structures are placed during generation, so pre-generating also removes first-exploration lag.

What You Need Before You Start

Install Chunky from its official sources, the plugin build for Paper, Spigot, or Purpur and the mod build for Fabric or Forge, then restart once. Chunky supports Minecraft 1.15 and later. Run it on a fresh world before publishing the address, because generating alongside live players competes for the same CPU. The maintenance-window rule also applies after an update that changes world generation.

• The overworld is the default target; the_nether and the_end need separate /chunky world passes.
• Pre-generate during maintenance or right after install, never at peak hours.
• Leave a few quiet minutes afterward so the chunk cache flush settles.

Choosing a Radius That Matches Your Border

The Chunky radius is measured in blocks while chunks are 16 by 16 blocks, so divide by 16 to get the distance in chunks. A radius of 1000 blocks is 62.5 chunks in every direction: 125 by 125 chunks, or 15,625 files, as a square, roughly 12,270 as a circle. Match the radius to your world border so players never reach ungenerated terrain. A radius of 500 blocks suits a small survival server; large communities commonly use 2000 or 3000.

Set a 1000-block square centred on spawn and start it:
/chunky center 0 0
/chunky radius 1000
/chunky shape square
/chunky start

Running Chunky, Including From a Command Block

The command set is small: /chunky radius sets the area, /chunky shape picks square or circle, /chunky start begins, /chunky progress reports chunks per second, and /chunky stop pauses. The same commands run from the console without the slash, and from a command block: a repeating command block inside spawn chunks firing /chunky start on boot restarts interrupted runs. A finished run reads 100% in /chunky progress and logs a done message.

Minimal full run from chat or console:
/chunky radius 1000
/chunky start
/chunky progress

Tradeoffs: Disk, RAM, and Timing

Pre-generation trades short-term CPU for disk and memory. Each region file holds up to 1024 chunks, so a 15,625-chunk square is about 16 files, controllable storage. RAM is the livelier cost: Chunky buffers chunks as it writes them. On Paper, tune the chunk-system section in paper.yml to cap flushing. Schedule the run for an upgrade window or launch, never a peak session.

• Disk: megabyte-scale region files, small but real on small plans.
• RAM: pause Chunky near peak memory or lower its thread count in config.
• Timing: do it at launch or in maintenance, then restart once afterward.
• After it finishes, set spawn and build out the spawn chunks too.