Overworld

The Overworld is the dimension in which all players begin their Minecraft journey.

Creation
The Overworld is created as the only dimension when the player creates a new world. (The other dimensions—the Nether and the End—aren't created until a player enters the corresponding portal.)

Seeds
A new world in Minecraft is generated through the use of a seed, which is an integer used as a starting point for the world generation formula. The player can specify a seed or allow the game to generate one randomly. If given a non-integer input (such as the word "Glacier"), the game converts it into a corresponding integer (such as 1772835215).

A given seed will generate almost exactly the same world every time, provided the same edition, game version, and world type are used. Although the exact spawn point varies, the coordinates of all terrain features will be the same. Seeds in Bedrock Edition, Education Edition, and New Nintendo 3DS Edition also generate identical worlds for the same version and world type, but these are completely different from the worlds generated by those seeds in the other editions.

Environment
The Overworld is an incredibly complex environment with a wide variety of features.

Biomes


The Overworld is divided into biomes of various types. A biome's type determines the basic characteristics of the terrain within it, and almost all of them have several variations that alter these characteristics to create more realistic terrain. The biome type also influences the biome's size, determines which mobs can spawn within it, and affects how environmental behaviors such as weather are expressed within it.

Natural structures


The Overworld is composed of a large number of terrain patterns, called structures, whose arrangement varies widely from one seed to another. The exact structures are unique to each world, while the types of structures that can be generated at a given place are determined by the biome type. Structures are meant to represent real-world equivalents such as mountains, caves, and lakes. "Impossible" (in the real world) formations, such as floating islands, can also be found throughout the Overworld.

Along with terrain features, natural structures include naturally-generated buildings, such as villages, dungeons, and mineshafts.

Day-night cycle


The Overworld is the only dimension with a day-night cycle, and thus, the only one where the environment reflects the passage of time. In contrast to time zones in the real world, Overworld time is universal; it is always the same time for every player in the dimension regardless how far apart they might be, even in an "infinite" world.

During the daytime, the sun acts as a powerful light source, with a light level of 15, the maximum. Sunlight is strong enough to grow plants and affect the way mobs spawn, among other interesting effects. During the nighttime, the moon is the only natural light source. However, moonlight is comparatively dim; the light level will fall to a minimum of 4, allowing hostile mobs to spawn. Other than during thunderstorms, nighttime is the only time players may sleep in a bed.

The day-night cycle can effectively be measured using a clock, which allows players to determine the approximate Minecraft time anywhere in the Overworld. Time can also be sped up with the use of the command.

The sun rises in the east and sets in the west, just as it does in the real world. Observing its motion is a simple method of telling direction without a compass.

Mobs
The Overworld is home to a wide variety of mobs. Mobs vary greatly in behavior and the level of danger they present to the player. Different mobs spawn at different times and places depending on the light level and the biome, among other factors. On occasion, a mob will move between the Overworld and another dimension, such as the Nether, by using a portal, but this is relatively uncommon. However, boss mobs like the ender dragon and the wither cannot enter portals.

Generation
As with all other dimensions in the game, the Overworld can generate infinitely. However, there are some limitations, as detailed below.

The Overworld encompasses a three dimensional volume that extends vertically from the build limit (y=256) down to the Void (y=0), and horizontally for a virtually infinite distance in each direction. This volume is filled (virtually speaking) with air, terrain, and structures. Technically, the terrain is formed by generating multiple noise maps to produce differing elevations, general land shapes, and complex mountain and cave systems.

Chunks


Chunks are the method used by the world generator to divide maps into manageable pieces. Chunks measure 16×16×256 blocks in size (16 blocks wide, 16 blocks long, and 256 blocks high), with a total volume of 65,536 blocks. Chunks are generated around players when they first enter the world, and additional chunks are generated as needed as they wander around it. Once generated, a chunk becomes a permanent part of the world and is saved with the game from then on.

The game doesn't keep all chunks loaded into memory all the time, because for a large world that could easily exceed the device's capacity. Instead, chunks are saved to external storage when all players have left the area they are in, and are reloaded again whenever a player approaches them later. The game only simulates activity (mobs spawning, trees growing, water flowing, dropped items disappearing etc.) in the loaded chunks, so this limits activity to the chunks that players can actually see and interact with, which makes the best use of the processor's power. Players can alter the number of blocks loaded by adjusting the render distance or simulation distance. (It should be noted that some chunks are never unloaded. These include the spawn chunks and chunks in ticking areas. Activity in these chunks occurs for as long as the world is open.)

When infinite worlds were first implemented in Java (Infdev - Beta 1.7), the chunks beyond block coordinates X/Z ±32,000,000 were treated as "fake"; blocks within them will still generate, but the normal physics properties will not be applied to them. As a result, if the player is within one of these "fake" chunks and tries to walk on these blocks, they will fall right through them into the void. These "fake" chunks no longer occur in more recent Java versions, and were never present in Bedrock Edition.

Limitations


While the world is virtually infinite, the number of blocks a player may physically reach is limited. Where the limits are depends on the edition of the game and the world type being played.

In Java Edition, the map contains a world border located by default at X/Z coordinates ±29,999,984. The world border is an animated wall of blue stripes. Standing near the border results in a red vignette appearing around the screen. Most entities are unable to pass the border, except by teleporting. Players who breach the border will receive constant damage unless they are in creative or spectator mode. The player can teleport past the world border and continue as far as X/Z ±29,999,999, where there is an invisible wall. However, the player can travel a few chunks further by riding horses, pigs, and minecarts through it. Once the player passes X/Z ±30,000,000, "fake chunks" will generate in which the blocks have no collision boxes.

In the Bedrock Edition, Old-type worlds are limited to 256 blocks each in the X and Z directions. The edge of the world is barricaded with an invisible barrier. Infinite-type worlds have no fixed horizontal limits, but either generation stops or normal game behavior begins to break down at extreme distances; the exact details depend on the platform. However, experiments suggest that players can generally reach at least X/Z ±12,550,000 before such problems occur.

In the Xbox 360 Edition, PlayStation 3 Edition, PlayStation Vita Edition, and Wii U Edition, the Overworld is limited to 864×864 blocks. Additionally, in the Xbox One Edition, PlayStation 4 Edition and Nintendo Switch Edition, the player is able to further select the size of their worlds, from Small (1024&times;1024), Medium (3072&times;3072), and Large (5120&times;5120, except Nintendo Switch Edition). The edges of these worlds are surrounded by an invisible barrier with an endless sea of water beyond it.

Naturally generated
"Naturally generated" includes blocks that are created through the world seed.

Naturally created
Naturally created means a combination of events that cause a new block to be placed by natural causes, not the player. Some of these blocks may also be created as part of world generation.

Structures
Same as naturally generated, but these blocks are only created with the "Generate Structures" option enabled.

Folder
In Java Edition, information on the Overworld is stored in the  folder of the   directory, with "worldname" being the name of your world.

Deleting the  folder will reset the Overworld, so that all player-made changes and buildings in that dimension will be undone.

Trivia

 * The maximum number of blocks that can be generated in the Overworld is approximately 921.6 quadrillion (9.216×1017) blocks, assuming a distance of 30,000,000 blocks in either direction.
 * The total area is about 8 times the surface of the Earth, or approximately the size of Neptune's surface.
 * This means that storing a filled world, with no entities or block entities, would require 3.6864 quintillion (3.6864×1018) bits (409 petabytes) for the block data alone, based on the fact that each standard block is assigned 4 bits of information.
 * By manually modifying the game, it is possible to generate the world up to 2,147,483,647 blocks (the 32-bit integer limit) in either direction.
 * A 1:1 (1 block = 1 meter) scale map of the Earth, built in Minecraft, would be 510.9 trillion (5.109×1014) blocks in size.
 * Assuming the map is only one block deep and uses 1 byte per block, its size would be approximately 475,800 GB (464.7 TB).
 * A Moon-sized map would be made of 37.95 trillion (3.795×1013) blocks.
 * Its data size would be 35,340 GB (34.52 TB).