Chunker

Chunker

Supported MC Versions:

• Minecraft/Paper 26.1.2
• Requires Java 25 or higher
• Older Java 21 / pre-26.1.2 server builds are no longer supported by 26.1.2 and newer

Supported Servers:

• Paper, Pufferfish, Purpur, Leaf, and Folia
• Bukkit/Spigot fallback paths are still present, but this build targets the modern Paper/Folia 26.1.2 API

Overview
Chunker is designed to be more efficient and resilient than traditional pre-generators. Many pre-generators track thousands of chunks in memory, risking significant rollback or data loss if the server crashes. Chunker, by contrast, only tracks minimal state, like iterator position, submitted progress, completed progress, and generation center, so crashes have less impact on the generation process.

It works best on Paper forks because it can utilize asynchronous chunk-loading ( CompletableFuture) for faster performance. Folia uses its region scheduler path. On non-Paper server paths, it falls back to synchronous chunk-loading behavior.

You can configure Chunker to run automatically only when there are no players online and to halt immediately if a player joins. This behavior is controlled by auto_run in settings.yml. You can also adjust how aggressively each dimension's tasks run by changing task_queue_timer and parallel_tasks_multiplier. If you want to keep the server load minimal, set low concurrency or run only when the server is empty.

Optimized JVM Launch Parameters (start.bat):

• Xms1G and Xmx30G should be updated to match your minimum (Xms) and max memory (Xmx) for your own server.
• Update both XX:ParallelGCThreads and XX:ConcGCThreads to match your number of threads.

Paper Config
In your paper-global.yml or equivalent, consider increasing the parallelism for chunk generation and I/O:

• Adjust io-threads and worker-threads to match, or approach, your CPU's thread count.
• By default, Paper may not use all available threads for chunk tasks. Raising these can help asynchronous chunk generation run at full speed.
• Lower region-file-cache-size if running pregen on a fresh world with no players online.

Command Usage

The primary commands are:

Examples

1. /pregen 4 10s minecraft:overworld default
   • Pre-generates the overworld (minecraft:overworld)
   • Uses 4 parallel chunk-loading tasks per scheduler cycle
   • Prints progress logs every 10 seconds
   • default uses the world border as the radius
2. /pregen 6 5s minecraft:overworld 1000b
   • Pre-generates the overworld
   • 6 parallel tasks
   • Prints logs every 5 seconds
   • 1000b = 1000-block radius, rounded to full region coverage
3. /pregen 16 5s minecraft:the_nether 2r safety