Introduction to Minecraft Worlds

A Minecraft World isn’t just a level.dat and some .mca chunk files - it’s more:

World Structure

someworld/
├── level.dat                                  - the most important and well known .dat file, contains world metadata and settings
├── level.dat_old                              - backup of level.dat, gets created every time you save the world
├── session.lock                              - for preventing simultaneous access to a world
├── icon.png                                   - world icon
├── data/
│   └── minecraft/
│       ├── custom_boss_events.dat             - contains bossbar data
│       ├── game_rules.dat                     - contains all game rules
│       ├── random_sequences.dat               - contains random sequence data for blocks that need deterministic randomness, such as spawners, or visual randomness, such as fire or leaves.
│       ├── scheduled_events.dat               - contains data for functions scheduled using /schedule
│       ├── scoreboard.dat                     - contains scoreboard data
│       ├── stopwatches.dat                    - contains /stopwatch data, stopwatches are measured in real time instead of ticks and are not affected by lag
│       ├── wandering_trader.dat               - contains wandering trader spawn delay
│       ├── weather.dat                        - contains weather data
│       ├── world_clocks.dat                   - contains tick data for specific worlds
│       └── world_gen_settings.dat             - contains world generator settings like the seed or the preset
├── datapacks/
├── dimensions/
│   └── minecraft/
│       ├── overworld/
│       │   ├── data/
│       │   │   └── minecraft/
│       │   │       ├── chunk_tickets.dat      - contains chunks that are force-loaded (you can trigger this using /forceload add ~ ~)
│       │   │       ├── raids.dat              - contains raid data for the world
│       │   │       └── world_border.dat       - contains world border settings like the size, damage-per-block or the warning-blocks
│       │   ├── entities/
│       │   ├── poi/
│       │   └── region/
│       ├── the_nether/
│       │   ├── data/
│       │   │   └── minecraft/
│       │   │       ├── chunk_tickets.dat      - contains chunks that are force-loaded (you can trigger this using /forceload add ~ ~)
│       │   │       ├── raids.dat              - contains raid data for the world
│       │   │       └── world_border.dat       - contains world border settings like the size, damage-per-block or the warning-blocks
│       │   ├── entities/
│       │   ├── poi/
│       │   └── region/
│       └── the_end/
│           ├── data/
│           │   └── minecraft/
│           │       ├── chunk_tickets.dat      - contains chunks that are force-loaded (you can trigger this using /forceload add ~ ~)
│           │       ├── ender_dragon_fight.dat - contains ender dragon fight data, e.g. how often he has been killed, open gateways or the dragon uuid
│           │       ├── raids.dat              - contains raid data for the world
│           │       └── world_border.dat       - contains world border settings like the size, damage-per-block or the warning-blocks
│           ├── entities/
│           ├── poi/
│           └── region/
└── players/
    ├── advancements/
    │   └── <uuid>.json                        - contains advancements for the player with the given uuid
    ├── data/
    │   ├── <uuid>.dat                         - contains more player data, like the inventory, position or the XP Level
    │   └── <uuid>.dat_old                     - backup of the player data
    └── stats/
        └── <uuid>.json                        - contains player statistics

Next steps

Now that you know how a world is laid out on disk, here’s where to go next with minified-worlds:

Opening a World

Load a world folder and read its level.dat, spawn point and other core settings.

Dimensions and Chunks

Understand how terrain is stored, and read or write chunks and blocks.

Entities and Points of Interest

Read and add the mobs, items and villager points of interest inside a chunk.