Overworld

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

Creation
The Overworld is created by default upon creating a new world. Other dimensions, such as the Nether and the End, will only be created upon accessing the proper portals.

Seeds
New worlds in Minecraft are generated through the use of seeds, which are typically a random number that is used as a starting point for the world generation formula. If given a non-integer input (such as the word "Glacier"), the seed input is converted into the corresponding integer (such as 1772835215).

Seeds will generate almost exactly the same world every time, given the same game version and the same world type. Although the exact spawn point varies, the coordinates of all terrain features will remain the same.

Environment


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

Biomes


The Overworld is subdivided into biomes. The current biome determines almost all physical aspects of the terrain. Biomes may vary widely based on size, and almost all biomes have several different variations of themselves. Biomes also influence which mobs may spawn, and affects environmental behaviors such as weather.

Natural structures
The Overworld is comprised of several unique terrain patterns, known as structures, that vary widely depending on the seed and the biome. While specific structures are unique to each world, they can be categorized by comparing them to a real-world equivalent, such as mountains, caves, and lakes. "Impossible" 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, time.

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. It is only during nighttime that 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 from any location in the Overworld. Time can also be sped up with the use of the command.

In the Computer and Console Editions, the sun rises in the east and sets in the west just as it does in the real world; in Pocket Edition it rises in the north and sets in the south. Either way, 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 may spawn depending on the light level and the biome, among other factors. They vary widely in behavior and the level of danger they present to the player. Mobs from other dimensions, such as the Nether, may use portals to enter the Overworld, and vice versa. However, boss mobs, such as 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 the height limit (y=256), down to the Void (y=0), and extends for millions of blocks in every direction on the horizontal plane. Technically speaking, the world is generated through a process which creates multiple noise maps to create differing elevations, general chunk 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 blocks wide, 16 blocks long, and 256 blocks high, for a total volume of 65,536 blocks. Chunks are generated around players when they first enter the world, and as they wander around the world, new chunks are generated as needed. By adjusting the render distance, the player can adjust the number of chunks that will be loaded into memory, ranging from 25 chunks up to 1089.

Only chunks within the set range may have activity (mobs spawning, trees growing, water flowing, dropped items disappearing etc.), while chunks outside of this range are inactive, and are stored on the disk; this type of management is required so that players' computers do not need to track hundreds or thousands of blocks and entities at once. Note that this does not apply to spawn chunks, which will always experience activity regardless of how far away the player travels.



Limitations
While the world is essentially infinite, the number of blocks the player may physically walk on is limited. The map contains a world border at +/- 29,999,984 X/Z. The world border is an animated wall of blue stripes; as you approach, the edges of the screen will tint red for several seconds. Most entities are unable to pass the border, except through teleporting. Players who breach the border will receive constant damage, unless they are in Creative mode.

In the Pocket Edition, Old worlds are limited to 256 blocks in either direction. The edge of the world is barricaded with invisible bedrock.

In the Xbox 360 Edition, PlayStation 3 Edition, PlayStation Vita Edition, and Wii U Edition, the Overworld is limited to 862&times;862 blocks. Additionally, in the Xbox One Edition and PlayStation 4 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). The edges of these worlds are surrounded by an endless sea of water, preceded by an invisible barrier.

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.

Technical information
Information on the Overworld is stored in the  file of the   directory, with "worldname" being the name of your world.

Deleting the  file 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 (9.216x1017) 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.
 * This means that a filled world, with no entities or block entities, would be 3.6864 quintillion (3.6864x1018) bits (409.27261579781770706 petabytes) in block data alone, due to the fact that each standard block is assigned 4 bits of information.
 * If someone made a 1:1 (1 block = 1 meter) scale version of the Earth, its area would be 510.9 trillion (5.109x1014) blocks.
 * Assuming the map is only one block deep and uses 1 byte per block, its size would be approximately 475,800 GB, or 464.7 TB.
 * A Moon-sized map would be made of 37.95 trillion (3.795x1013) blocks.
 * Its data size would be 35,340 GB, or 34.52 TB.