World boundary



The world boundary is the area at the edge of the Minecraft world.

Definition
The boundary of the world has several "layers".

The first layer is the world border, which lies at X/Z ±29,999,984 by default, and establishes an arbitrary blockade to prevent the player from advancing. There are several methods of bypassing this border.

The second layer lies exactly one chunk further, at X/Z: ±30,000,000. At this point, there is an invisible wall preventing the player from advancing, even in spectator mode. Using commands like does not work, since the game does not accept any value beyond X/Z: ±30,000,000. Other block interactions, such as TNT exploding or water flowing, affects blocks outside this limit. By using a minecart (in a superflat preset with the top layer as rails), the player can go even further, up to X/Z: ±30,000,496. At that point, the player is frozen in place until the minecart is destroyed, then they are teleported back to X/Z: ±30,000,000.

The third and final layer lies at X/Z: ±30,000,496, which can be considered the absolute edge of the Minecraft world, as chunks no longer generate beyond this point. This value is hard-coded into the game's source code, so it's impossible to advance past this point without the use of modifications.

The maximum possible height is 1.798×10308 (or 21024), the limit where mathematics break down in the game's code. In attempting to teleport beyond this limit, the game interprets the number as infinity and refuses to carry out the teleportation.

By editing the source code for the game, it is possible to extend the terrain generation and world border past X/Z: ±30,000,240 (up to X/Z: ±2,147,483,647) and experience the game quite normally (no ghost chunks; mobs can spawn alright; commands accept higher values). The game performs normally even at distances of X/Z: ±1,000,000,000. At greater distances, block lag starts to become noticeable, and mobs begin behaving very strangely. A hard limit exists at X/Z: ±2,147,483,647&mdash;the mathematical limit of a signed 32-bit integer&mdash;and attempting to travel or load chunks near here simply causes the game to crash. It is advisable to set the world border to at most several hundred blocks before this limit. Lighting ceases to work past 2 and everything becomes absolutely dark unless with the night vision effect. Entering a nether portal at this point would teleport the player to X/Z ±268,435,455 (2 − 1) in the nether.

Effects
Generally, long server response times caused by massive distances produce unintended results, but most blocks and entities behave normally, with a few exceptions:


 * Beyond the X/Z 30,000,000 mark:
 * Mobs do not spawn at all.
 * Lighting does not update (with exception to sunlight and moonlight).
 * Items may jitter slightly.

Beyond this, most of the unintended behavior of blocks and entities is caused by the world border (as detailed here, rather than the massive distances of the boundary itself.

Cause
Though the reason for the world boundary is still controversial, it may have to do with the way Minecraft generates and loads chunks in the game. When the game generates its terrain, it uses something called 3D Perlin Noise. This is a noise map that shows how high or low Minecraft blocks generate. When the game generates the terrain, it creates a noise map of all the terrain that cannot be interacted with at all. Then, Minecraft would load in the chunks after the basic frame was in place. When the game generates chunks out to X/Z: 30,000,000, for some reason the game cannot load chunks beyond this point. However, the terrain noise map has generated the terrain all the way out to X/Z: 2,147,483,647. So Minecraft still generates the terrain noise map, but not the blocks themselves. So what we get is empty terrain that has the textures for the terrain that should be there.

Trivia

 * Traveling from one edge of the world to the opposite edge by powered rail would take 35 days and 10 hours. Building the rails for such a trip would require enough iron and/or gold to fill over  723 double chests, even when packed into blocks, as well as sticks made from enough wood to fill over  135 double chests (as log blocks, not as planks, and excluding the redstone torches). (53 stacks of logs would be required just to make enough chests to hold all the building materials for this rail track.) If already crafted, the rails required would fill  17,361 double chests. If the player had to gather the materials to make all those rails, they would wear out  14,404 diamond pickaxes and  300 diamond axes (on average, about  3,601 diamond pickaxes and  75 diamond axes, both enchanted with Unbreaking 3).
 * Even if one were to amass all these materials, actually laying said track would require the player to travel the entire distance through other means anyway.
 * Factoring in the need for powering the track and assuming the player were to use redstone torches, the player would require 3,529,412 torches for the full track, since a torch can optimally light 17 blocks. That requires 55,148 sticks and bits of redstone dust, which requires 2042 large chests, which requires 128 stacks of log blocks to make the chests (which requires 3 large chests).
 * Traveling from 0,0 to the edge of the world by foot takes around 140 days.
 * It is possible to generate trees and vegetation beyond 30,000,000 by loading a version of Minecraft after Java Edition 1.9, then load a few chunks beyond the world border. Then, close the world and load a version of Minecraft between Beta 1.8 - Release Java Edition 1.6-pre and load the same world. If the players travel to the world barrier, there are a few chunks that generate beyond 30,000,000 that have trees and grass.
 * It is possible to even generate Far Lands chunks using this method. Load a world in release Beta 1.8 - Release 1.6 and teleport to X/Z: 30,000,000. Close the world before the fake chunks generate and load the world in Beta 1.7.3. The Far Lands chunks load and then, the player can load as many chunks as they want. Then close the world and load it in a newer version, and the player has Far Lands chunks in the 30,000,000 block area.
 * Spiders can climb the border, continuing to climb upward indefinitely.