[📦] No Unused Chunks

This Minecraft mod reduces world size by discarding unused chunks. In other words, any newly generated chunks that the player or an entity or a block hasn't interacted with will not be saved, and that will therefore reduce the world size. Works in both singleplayer and on dedicated Minecraft servers.

Important: Please back-up your world if you are planning on using this mod on an already existing world. This mod shouldn't cause any issues, but it is still a good idea to back-up worlds, just in case. Also, Mod Menu and Cloth Config API are optional dependencies.

How does the mod work? (automatic chunk discarding)

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(Note that this feature can be disabled in the config)

Every chunk in a world has a special flag called "needs saving". The game uses this flag to keep track of whether any changes were made to a chunk. When this flag is set to "true", the game will then save the chunk the moment it gets unloaded. The game does this in order to save performance by avoiding saving chunks that had no changes made to them.

As soon as the game generates a new chunk, that chunk is then immediately marked as "needs saving" by the game, causing the game to save those chunks the moment they get unloaded. This is very likely done to save performance by avoiding generating the same chunks every time a player comes in their range.

This mod overrides the rule above, and unflags newly generated chunks as "needs saving" anyways, causing them to not be saved once they get unloaded, unless a change is made to those chunks. This ends up shrinking the world size at the cost of performance, because the next time a player comes near those chunks, they will have to be generated again.

How well does the mod do?

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You can find that info on the GitHub page. The CurseForge description formatting is not letting me properly place the code block here.

The trade-off (for automatic chunk discarding)

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Doing what the mod does has it's own trade-offs, the main one being performance. By not saving newly generated chunks, they will have to be re-generated every time a player comes near them, or whenever the world is loaded once again. Generating chunks of course costs performance and takes time for the game to do, and the higher the render distance, the more performance it will cost.

It is because of this trade-off that the `UNFLAG_CHANCE` config property was introduced into the mod. This property defines the percentage of chunks that will be affected by the mod. By default, 100% of newly generated chunks are unflagged. Decrease this value to increase the world generation performance, but keep in mind that that will increase the world size as well.

Can the mod remove unused chunks generated before the mod was installed or while the mod was disabled?

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As of v1.2, it finally can. The feature works by removing chunks no player has ever visited. Because of this, it is not recommended to use this feature on chunks that somehow got modified without having an in-game player visit those chunks. For example, if you used world editing software to modify chunks of a given world, there may be a chance those chunks get removed by this feature anyways, as there are no other ways for this mod to know which chunks it shouldn't erase, other than looking at how long a given chunk was inhabited by a player for.

How to use the feature (Minecraft client):

• Go to the world selection screen
• Select a world and click on "Edit"
• Click on "Optimize World"
• Check the "Remove uninhabited chunks" checkbox
• Click on "Create Backup and Load".
• It is advised not to click on "I know what I'm doing". Instead, back up the world, make sure chunks got removed properly, and if they did, only then you should discard the backup.

(For <v1.2) Unfortunately it can not.

Configuring the mod

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There are several ways to configure the mod. The main way of configuring it is by going into the config directory and creating a nounusedchunks.properties file. To see the list of properties you can use, please visit the GitHub page. The CurseForge description formatting doesn't display code blocks properly.

Mod Menu and Cloth Config API
The easier way of configuring the mod is to install the Mod Menu and the Cloth Config API mods, and then use those mods to configure this mod in a settings menu while the game is running. Those mods are not required to run this mod.

A showcase of removing unused chunks

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This video shows how the mod can be used to remove "uninhabited" chunks to reduce world size: