Custom World

A custom world is a world created with or modified to include any or all of several optional rules and processes. While some options were available earlier (particularly on servers), general availability was introduced with version 1.6.1.

There are two types of custom world options: creation and post-creation.

Creation options

Setting the world size is available without invoking custom rules, but can only be selected during world creation. Worlds can be created at 1/16, 1/4, 1x, or 4x size (a 1x size world is normal and default) without invoking customized rules.

If custom rules are enabled during creation, the following options are available:

Seed (random or custom, the latter requests typing in text to use as a seed for the randomization process)
Oceans (no oceans, small oceans, normal, large oceans, ocean world)
Temperature (very cold, cold, normal, warm, hot, very hot)
Rainfall (very dry, dry, normal, wet, very wet)
Plants (no plants, few plants, normal, more plants)
Trees (no trees, gem trees only, sky island trees only, few trees, normal, more trees)
Terrain (totally flat, quite flat, normal, mountainous)
Caves (no caves, normal, more caves)
Lakes (no lakes, normal, more lakes)
Sky Islands (no sky islands, fewer sky islands, normal, more sky islands)
Ore Quantity (no ore, less ore, normal, more ore)
Ore Distribution (small veins, normal, large veins)
Gems (no gems, fewer gems, normal, more gems)
Treasure (no treasure, less treasure, normal, more treasure)

Post-creation options

Worlds created without customized rules can be modified to include them, but the options available during creation will not be available. Any world using customized rules does have access to the following options, accessible through the Pause Menu, which can be changed at any time:

Health (one hit kill, hard, normal, easy, infinite health)
Hunger (hungrier, normal, fuller, always full)
Happiness (sadder, normal, happier, always happy)
Clothing Decay (no decay, slower, normal, faster)
Tool Decay (no decay, slower, normal, faster)
Death (no death, no RIP, normal, no regeneration, die on exit)
Max Blockheads (1-5)
Spawn Items (slots 1-7; default, empty, custom count 1-99 and item similar to a trade portal)
NPC/Mob Difficulty (hard, normal, easy, passive)
Trade Portals (normal, disabled, buy only, everything free)
Day/Night Cycle (slower, normal, faster)
Sun Color (adjust Red, Green and Blue values from 0.0 to 2.0, normal is 1.0 for each)
World Modification (enabled, admin only, disabled)

Limitations

Any world created with or modified to include custom settings cannot be changed back to a normal world. They also will not allow mining of time crystals (and will not spawn them if customized during creation) and will not allow the crafting, placement, or use of portal chests. Transactions through a trade portal in a customized world do not affect the global market.