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.

Generated Structures
The Overworld contains numerous generated structures, at a wide variety of scales.

Terrain
Biomes dictate the shape and height of the world. At this stage, the ground is made mostly of stone and stone variants, with water filling in most empty spaces below layer 63, with exception for structures.

Mountain
Mountains are hills with extreme slopes and cliffs. Mountains can sometimes have caves through them. On an amplified world, mountains are extremely common in all biomes except ocean and swamp biomes.

Floating "island"
Floating "islands" are structures that float in midair that are not connected to the ground, the sea, hills or cliffs. Floating "islands" are normally just random pieces of floating dirt and stone found near cliffs, but on rare occasions they can be large, floating structures that even have springs and trees on them. Floating Islands are most frequently found in mountains biomes (and its variants), along with the "hills", "mountains", and "modified" variants of most biomes, especially shattered savannas.

Hollows
Hollows are the opposite of floating islands. They look like caves, but they have nothing to do with cave generation (although they may intersect with them). When there are many overhangs, they close together and create a hollow. They have exactly the same floor as the terrain above, depending on the biome that they are located in, unlike caves. Hollows have no specific floor. Grass blocks can generate inside too, and interestingly will survive without light. When they generate under the sea level, they are filled with water. They are extremely rare in the default world, but can be found far more commonly in certain customized worlds.

Hill
Hills are randomly generated pieces of land in the map. Like stairs, hills are always traversable to their lowest point by virtue of the algorithm which generates them; there is almost always a place on each level from where the next level can be accessed, meaning that the player can climb a hill one level at a time until they reach the top. Cases where this is not true are rare.

Surface layer
The uppermost layers of the terrain are converted to a biome-dependent material: usually grass blocks and dirt, or sand in deserts and beaches. Podzol is found in giant tree taiga, mycelium in mushroom field biomes, and red sand is found in the badlands biome. Sandstone is generated under sand.

Basin
Occasionally, instead of being converted to dirt or sand, the top layer is stripped away, leaving a 'basin' of bare stone. They bear some resemblance to a geological 'shield' (an area of tectonically stable rock that has been exposed to prolonged erosion due to its very old age; it is distinct from the geological term "basin"). They seem to be more common in forest or plains, and are occasionally seen filled with water. Commonly, minerals can be found in these, generally coal ore and iron ore. If generated in a Badlands biome, gold ore can also be seen.

Lake
Lakes are shallow and often small bodies of liquid. Water lakes, which are small pools of water springs, can generate above sea level or inside caverns. They can also generate isolated underground, connected to no other structures whatsoever. When in a cold biome, these small lakes are never initially frozen but will turn to ice if exposed. The lakes can also be composed of lava; however, lakes of lava are much rarer. Lava lakes found at the surface are surrounded by stone (which can be replaced by ore veins such as dirt, gravel and coal). Both types of lake generate with a small air pocket above them, which may result in floating sand, floating snow cover or even the top two-thirds of trees above the lake. Lava lakes may cause trees to burn away.

Mineral vein
A mineral vein is a natural deposit of ores. Players can come across these veins in caverns or anywhere where there is natural stone. Underground deposits of dirt and gravel are generated in this step, followed by the more precious ores: coal, iron, gold, redstone, diamond, emerald (in mountains biomes) and lapis lazuli. They can only form in stone, and do not replace each other or any other block. However, there is one exception: other ores can replace andesite, diorite and granite. Note that two or more mineral veins can form next to each other and make it look like a mineral vein made of more than one material.

Spring
Springs are randomly generated blocks of either lava or water that act as a source of their respective material. While both can be found on the vertical side of stone blocks above the surface, lava springs are more often found underground beneath layer 32 in caverns and mineshafts. They do not generate above a certain Y altitude.

Mossy cobblestone boulder
These structures are meant to represent boulders, made entirely of mossy cobblestone. The arrangement of these structures varies greatly. They can be found dotted around areas of the giant tree taiga biome. Mossy cobblestone boulders are quite rare, due to the giant tree taiga biome's rarity.

Ice spike
Ice spikes are tall spires made of packed ice that can only be found in the snowy tundra biomes. There are two variants of ice spikes: one is short and thick, and the other is extremely tall and thin.

Iceberg
Icebergs are structures that generate in frozen oceans and their deep variants. They consist primarily of packed ice with a little bit of ice and blue ice, and will often be topped with snow. They are the only place where blue ice can be found naturally. Icebergs generate in a wide variety of shapes and sizes, ranging from small "islands" to giant mountain-like ice structures. They can also generate with "cave-like" holes in them, which sometimes reach to the other side of the iceberg. Polar bears and strays can also spawn here, much like other cold biomes.

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 surface area of the planet Neptune.
 * 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).