Pre-Generating and Trimming Worlds in Minecraft – 2025 Guide

If you're running a Minecraft server, especially one with a large world or heavy player activity, pre-generating and trimming chunks can significantly improve performance. This guide will walk you through both processes for Spigot/Bukkit and Forge/modded servers, using plugins like WorldBorder and mods like Chunk-Pregenerator.

🧱 What is Chunk Pre-Generation?

By default, Minecraft generates world chunks as players explore new areas. Pre-generating means generating these chunks in advance, so the server doesn’t have to work as hard during gameplay. This reduces lag and provides smoother performance during peak hours.

⚠️ Warning: Chunk pre-generation is CPU and RAM intensive. Run it when no other players are online.

🧹 What is Chunk Trimming?

Chunk trimming removes any world data outside your chosen world border. This helps reduce:

• Unused region files
• Server storage usage
• Backup sizes

Trimming won’t delete anything within your set border—it only clears chunks you’ll never need.

✅ Requirements for Spigot or Bukkit Servers

To follow this method, you’ll need:

• A Spigot or Bukkit-based server
• The latest version of the WorldBorder plugin
  • v1.8–1.12
  • v1.13–1.14
  • v1.15–1.16
• At least 2 GB RAM for larger pre-gen sizes

🔧 How to Pre-Generate Chunks (Spigot/Bukkit)

1. Install the WorldBorder plugin
2. Restart the server
3. Stand at your spawn or centre location (usually 0,0)
4. Set the border:
   • /wb set <radius> for a square
   • /wb set <radiusX> <radiusZ> for a rectangle
5. Whitelist yourself and ensure you're the only one online:
   • /whitelist on
6. Start generation:
   • /wb fill
   • /wb fill confirm

You’ll see progress updates like this:

7. Cancel at any time:
   • /wb fill cancel
   • or pause with /wb fill pause
8. Optional: Trim the world to your border:
   • /wb trim
   • Only run this when you’re the only player online

📸 Before and After Chunk Trimming

Here’s what trimming looks like visually:

Before and After Pre-Gen (WorldBorder):

Chunk Trim Comparison:

🔥 For Modded Servers (Forge)

Running a Forge server with terrain mods? Chunk pre-generation is even more valuable due to the increased worldgen complexity. You’ll use the Chunk-Pregenerator mod.

Requirements

• Server must be offline
• A manual backup is strongly recommended
• Compatible Forge version: 1.4.7 to 1.16
• At least 2 GB RAM
• Download the correct version of Chunk-Pregenerator

⚙️ How to Pre-Generate Chunks (Modded/Forge)

1. Install Chunk-Pregenerator on your server
2. Restart your server
3. Stand at your desired spawn/centre location
4. Run the command:bashCopyEdit/pregen gen startradius SQUARE 0 0 100
   
   • Replace 100 with your desired radius
   • Use CIRCLE instead of SQUARE to change the shape
5. The mod will show chunk-by-chunk progress
6. On completion, it will give a full summary including total chunks generated and any failures
7. For more commands and usage:
   Chunk-Pregenerator Command Documentation

🎯 Final Tips

• Always pre-gen when no players are online.
• Trim after pre-gen to keep your world clean.
• Don’t attempt this on a weak host—allocate enough memory and CPU threads.
• Back up your world before trimming or pre-generating.