World border

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

Appearance
The world border appears as animated, diagonal, narrow stripes. When the border is not moving, the stripes are a translucent aqua color. If the border is expanding, the stripes appear green; if the border is shrinking, the lines appear red.

Size
The world border is essentially a giant bounding box; by default, its center lies at coordinates X/Z: 0, with a width and length of almost 30 million (29,999,984) blocks from both ends. Its effects cease at an altitude of approximately Y=2^31-1 (2.147 billion, or 2,147,483,647), even though it no longer visually displays below Y: 0 and 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 dimensions. If it is in the Nether, it will appear red, regardless if the border is expanding or shrinking.

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 will float in midair; if an item is dropped from the player inventory, the item will fall normally.

If a mob is spawned from a dispenser via a spawn egg, the mob will behave 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) will take constant damage as long as they are outside the border.

While players themselves cannot move through the world border, 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
 * Mounting a minecart, boat, horse, or pig
 * Using commands such as.
 * Sleeping next to the world border

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



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

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 29999984. The border will still grow or shrink and the animation will display 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 29999984. The border will still grow or shrink and the animation will display 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 amount of blocks a player may safely be outside the world border before taking damage. The default is 5 blocks.
 * Sets the amount 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 will reach the player within the specified time. The default is 15 seconds. The tint will not display if the user is using fast graphics.
 * Causes the screen to be tinted red when a contracting world border will reach the player within the specified time. The default is 15 seconds. The tint will 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 will 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 will 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.

Trivia

 * The reason the default world border is at X/Z ±29,999,984 is because Dinnerbone put it 1 chunk (16 blocks) short of the edge to prevent falling through the world.