World border

The world border is the current edge of a Minecraft dimension.

Appearance
The world border appears as a series of animated, diagonal, narrow stripes.

The world border is tinted depending on how and if its size is changing. By default, when the border is not changing, the stripes are a translucent aqua color. If the border is expanding, the stripes appear green; if the border is shrinking, they appear red.

The world border appears different depending on the current graphics setting, which is very likely not intended; on Fast and Fancy it appears as light and translucent, but on Fabulous! it appears considerably darker.

Size
The world border is essentially a giant bounding box; by default, its center lies at coordinates  above Y: 255''.

With commands, the size and position of the border can be modified. The world border always behaves in full block increments, even if it is set to a partial block. Its default size and location remain the same across all three default dimensions. Custom dimensions can have individual sizes.

On entities
Most entities, with exception to some projectiles, are unable to move through the world border.

If a dispenser or dropper is placed so that it directly faces the edge of the border, then items, projectiles, TNT, etc. can be fired outside of the edge of the border. Any items fired out of a dispenser float in midair; if an item is dropped from the player inventory, the item falls normally.

If a mob is spawned from a dispenser via a spawn egg, the mob behaves normally. Spiders can climb the world border, and endermen can teleport outside of it.

Any players on the outside of the world border (with exception to those in Creative or Spectator mode) take constant damage as long as they are outside the border. The amount of damage depends on the distance to the border.

While players themselves cannot move through the world border, even if they manage to go ahead of chunk loading, they can reach the other side of the world border through other means, including:
 * Letting the world border pass them as it is shrinking
 * Throwing an ender pearl through the world border
 * Consuming chorus fruit near the world border and being teleported beyond it.
 * Dying and respawning, if the spawn point is outside the world border

Entities cannot spawn naturally outside the world border. They persist without taking damage if they spawned before the world border gets shrunk by a command.

On blocks
Players cannot normally place and destroy blocks, nor interact with objects outside of the world border, as there are no hitboxes. It is possible to place blocks outside of the world border, either by placing the block against one that is inside the world border or by using commands.

Most blocks still function outside the world border, and most redstone contraptions still function as well. Exceptions include falling blocks (such as sand and gravel), which drop as an item, and pistons or hoppers, which simply don't function. Explosions from TNT and other sources also work normally, destroying terrain outside of the border. Light from torches and other sources also remain unaffected.



Liquids can flow through the border and continue flowing until reaching their flow limit. Liquids cannot be placed on the outside of the border. Liquids placed via a dispenser flow as normal. Mixing water and lava with a dispenser results in the flow of each liquid abruptly ending, presumably because the stone, cobblestone, or obsidian that would normally generate does not.

When set to invalid values
The world border size can be changed by manually editing the level.dat file. In any case, there remains a world boundary at 30 million blocks on both the X and Z axes.
 * When set to 0 or a negative number, the entire world is treated as outside the world border, and the border warning overlay appears throughout the world. No blocks can be mined and entities take damage unless they are within the border safe zone.
 * When set to NaN, the entire world is treated as outside the world border, but no border warning appears. No blocks can be mined, even in Creative mode, although entities do not take damage.
 * When set to infinity, the border occurs normally.

Commands

 * Set
 * Sets the border to a square region with the specified size in blocks as the width and length. Optionally, a timeInSeconds may be specified such that the border grows or shrinks from the previous width to that being set over the specified time in seconds. If timeInSeconds is not specified, the world border changes immediately. To reset the world border size, set sizeInBlocks to 59,999,968. The border still grows or shrinks and the animation displays even if the game is paused.
 * Sets the border to a square region with the specified size in blocks as the width and length. Optionally, a timeInSeconds may be specified such that the border grows or shrinks from the previous width to that being set over the specified time in seconds. If timeInSeconds is not specified, the world border changes immediately. To reset the world border size, set sizeInBlocks to 59,999,968. The border still grows or shrinks and the animation displays even if the game is paused.


 * Center
 * Sets the center of the area inside the world border to the specified  and  coordinates. Tilde (~) can be used as a relative coordinate. To reset the world border center, set both  and  to 0 (zero).
 * Sets the center of the area inside the world border to the specified  and  coordinates. Tilde (~) can be used as a relative coordinate. To reset the world border center, set both  and  to 0 (zero).


 * Add
 * Adds or subtracts sizeInBlocks to/from the current world border width and length. sizeInBlocks may be a positive or negative number. Optionally, a timeInSeconds may be specified such that the border grows or shrinks from the current width to that being set over the specified time in seconds.
 * Adds or subtracts sizeInBlocks to/from the current world border width and length. sizeInBlocks may be a positive or negative number. Optionally, a timeInSeconds may be specified such that the border grows or shrinks from the current width to that being set over the specified time in seconds.


 * Damage
 * Sets the number of blocks a player may safely be outside the world border before taking damage. The default is 5 blocks.
 * Sets the number of blocks a player may safely be outside the world border before taking damage. The default is 5 blocks.


 * Sets the amount of damage a player takes when outside the world border plus the world border buffer. The default is 0.2 damage per second per block.
 * Sets the amount of damage a player takes when outside the world border plus the world border buffer. The default is 0.2 damage per second per block.


 * Warning
 * Causes the screen to be tinted red when a contracting world border reaches the player within the specified time. The default is 15 seconds. The tint does not display if the user is using fast graphics.
 * Causes the screen to be tinted red when a contracting world border reaches the player within the specified time. The default is 15 seconds. The tint does not display if the user is using fast graphics.


 * Causes the screen to be tinted red when the player is within the specified number of blocks from the world border. The default is 5 blocks. The tint does not display if the user is using fast graphics.
 * Causes the screen to be tinted red when the player is within the specified number of blocks from the world border. The default is 5 blocks. The tint does not display if the user is using fast graphics.


 * Get
 * Returns the current width of the world border.
 * Returns the current width of the world border.

World data

 * level.dat
 * : center of the world border (X-axis)
 * : center of the world border (Z-axis)
 * : damage taken per block moved outside the world border
 * : distance in blocks of the buffer zone where damage is not taken when outside the world border
 * : world border diameter
 * : maximum distance away from the border where the border warning overlay appears on the player
 * : time in seconds until the border warning overlay appears
 * : maximum distance away from the border where the border warning overlay appears on the player
 * : time in seconds until the border warning overlay appears
 * : time in seconds until the border warning overlay appears

Trivia

 * The reason the default world border is at X/Z ±29,999,984 is due to the fact that Dinnerbone put it 1 chunk (16 blocks) short of the edge to prevent falling through the world.
 * Despite this, it became impossible to fall through the world at high distances in early 1.7 development, over half a year before the world border's implementation.
 * Were a Minecraft world wrapped around with the borders together, the resulting planet has a circumference of 60000 kilometres or 9549 kilometres in radius, twice as large as Earth.