Chunk

A chunk is a section of the Minecraft world that is 16 blocks wide, 16 blocks long and as tall as the whole world. The server never loads the entire map at once; it loads, generates, ticks and saves it chunk by chunk.

Loading and generating

When a player moves, the server loads the chunks around them. If a chunk has never been visited, it has to be generated first from the world seed, which is one of the most expensive things a server does. Players exploring new terrain, especially with fast travel like elytra, can therefore cause more lag than players staying in built-up areas.

How many chunks are involved depends on two settings:

• View distance: how far chunks are sent to players.
• Simulation distance: how far chunks are actively ticked.

The number of chunks grows with the square of the distance, so small changes have a big effect.

Saving

Chunks are stored in region files (.mca) inside the world folder. Each region file covers 32 by 32 chunks. More explored terrain means more region files and a larger world on disk, which also makes backups bigger.

Why it matters for server owners

Chunk loading and generation affect CPU load, RAM use and disk size at the same time. Farms and machines only work while their chunks are loaded and ticked, which is a common source of player questions.

Practical tip

Pre-generate the world before opening a server. Plugins or mods such as Chunky generate terrain within a set radius ahead of time. It takes a while once, but players then load existing chunks instead of generating new ones, and you can set a world border so the world does not grow without limit.