For technical reasons, Aternos servers have a storage limit of 4 GB. A large portion of this storage can often be occupied by world files. Minecraft generates thousands of chunks around players, and saves them, even if no player has ever entered them.
To make sure your server stays within the storage limit and improve load times, the Optimize option for worlds is provided. If enabled, Aternos will automatically detect and remove unused chunks from your world.
When should I enable it?
World optimization is generally compatible with all Minecraft worlds. Even modded worlds with custom blocks, items and biomes will work without a problem.
The option should only be disabled if you want to use a world that was generated using external software (e.g. WorldPainter worlds or custom generated Maps of the Earth).
We will also try to detect incompatible worlds and disable the option automatically.
How does it work?
Our system uses the inhabitedTime value Minecraft saves for each chunk to determine whether it is used or not. This value is steadily increased for all chunks within a 5 chunk radius around a player and normally used to control mob spawning. If the value is 0 for a chunk, we can be certain that no player ever came near it and delete it safely.
You can find our world optimization software on GitHub: https://github.com/aternosorg/thanos