Bedrock

Bedrock, otherwise known as Adminium or other variations, is both an indestructible and unmineable block. The primary function of bedrock is to create an impassable barrier at the bottom of the Overworld and at the top and bottom of the Nether. It can also be found at the sides of the Nether in the Xbox version.

Obtaining
Bedrock is impossible to obtain without mods or Creative Mode. If placed on ground or objects, it can never be removed without using mods or Creative Mode.

In SMP or if the "cheats" option is turned on, Bedrock blocks can be obtained by using the /give command, but they cannot be removed once placed without creative mode.

Destructibility in Survival
It is a common myth that Bedrock can be destroyed by a sufficient quantity of TNT. Examinations of the Minecraft code have shown that multiple explosions do not add damage to blocks; any block that is not destroyed by one TNT immediately adjacent to it will not be destroyed by additional TNT. While Bedrock does have a finite damage resistance, there is no explosive in the game which has that much force (the average block having a resistance of 15-30).

Notch confirmed on the 11th of February 2011, during a Machinima Live stream, that it is indestructible, or so solid that the amount of TNT it would take to destroy it would more than certainly crash the game, therefore the save file would show no evidence of the explosion ever happening.

It is impossible to break Bedrock by hitting it. Bedrock has "hardness" of -1. A negative hardness is handled separately in the code, and causes any damage done to the block by the player's "hits" to be zero, and thus the accumulated damage will always stay at 0.

In Pocket Edition, if you activate a nether reactor on a low enough layer, the last layer of bedrock is replaced with netherrack, allowing access into the void in survival.

Creative
In creative mode, bedrock can be destroyed in one hit, just like any other block. By doing this, the Player is able to enter The Void but will die. This is one of the two ways to die in Creative Mode, aside from the /kill command. Bedrock still has an infinite blast resistance, therefore it is impossible to break it with TNT. Bedrock can also catch on fire.

In the Xbox 360 Edition version of Creative Mode, Bedrock can still be destroyed, however the final layer of Bedrock cannot be broken.

In creative mode on Pocket Edition, Bedrock can be broken, and then you can fly in the Void underneath; however, you still cannot place blocks underneath. There is no Void, and you will see the sky.

Classic


In Singleplayer Survival Mode, Bedrock is impossible to place without a mod, because Bedrock is never directly placed. But, using a server command on multiplayer, other blocks can be changed into Bedrock. Any Bedrock that exists on the map cannot be destroyed by the player.

In Multiplayer mode, server ops can place Bedrock blocks by using the "/solid" command. When /solid is used, stone blocks turn to Bedrock a short time after being placed. If /solid is used again, stone blocks placed will remain stone blocks. Normal players cannot place Bedrock; this makes Bedrock useful for making spawn jails. However, ops can destroy Bedrock like any other block, as a flag is set on the client when they log in. Vats of fluid blocks (water and lava) are also recommended to have Bedrock barriers so as to prevent server floods. Bedrock is used as a dark colored building material for normal structures as well.

A player can use an inventory editor to put Bedrock blocks in their inventory. If they attempt to place the blocks, the server will automatically kick them, even if they are an op. This is one of Notch's anti-griefing features scripted into server software.

In all Classic maps, the very edges of a map are lined with a Bedrock-textured barrier. This barrier is not actually made of Bedrock blocks; it is simply a flat, impassible wall with the Bedrock texture. It is also completely covered in water. Consequently, attempting to place blocks on it does not work; you must place a block on one already attached to the wall. This barrier appears on the sides of a map starting two blocks below ocean level, extends under the ocean, and across the entire bottom of the map. Additional walls made of Bedrock blocks are often built against the ocean to prevent flooding in custom servers. Using a /kill command for classic servers causes your player to go extremely far away from the map and to glitch high above the bedrock area. The command is highly glitchy, somehow being able to send you off the map.

Present
In Survival Mode, Bedrock appears on the very bottom 5 layers of a map and also at the top and bottom 4 layers of The Nether. It generates in a very rough pattern in both the Overworld and The Nether. In the Overworld, there are actually 5 layers even though it seems as if there are 4, this is because the lowest one you see is normally entirely Bedrock with little or no gaps. The lowest layer of Bedrock is layer 0, the highest is layer 4. It can also be seen at the top of the Nether, preventing you from going past layer 127. When you defeat the Ender Dragon a portal with a Bedrock frame appears. A single piece of Bedrock will appear after destroying an Ender Crystal.

Layout and position
Bedrock can be found at the bottom of the map in five different layers. The Nether also has a Bedrock bottom as well as a Bedrock top ("top" is now only in the middle due to the doubled map height). On occasion, mushrooms will spawn on top of Bedrock in the Nether. Bedrock can be found in the End, but not at the bottom of the world, instead at the top of the obsidian pillars and as part of the exit portal after the Ender Dragon dies.

Void fog


Void fog was added in the Beta 1.8 update so that The Void would appear black instead of sky color. This black fog (with gray particles floating in it) thickens as the player reaches Bedrock levels, regardless of render distance settings. See the graph (right) for the maximum view distance due to the fog.

All layers below Y=28 have some degree of void fog, unless an area is exposed to the sky. Opening up an area to the sky removes void fog in a small area around the opening.

On Superflat worlds the void fog is removed; otherwise, you wouldn't be able to see anything at all. This is why on Superflat worlds the void is the same color as the sky until you enter it.

In Creative mode, there is no void fog at all. Void fog can be toggled on and off in the Xbox 360 Edition.

Trivia

 * As of 1.5, TNT minecarts will immediately explode once hitting bedrock, even if not primed.
 * The Bedrock texture is modified from Stone, at a higher contrast and placed on all sides.
 * In Minecraft: Pocket Edition, Bedrock has a second form defined in the code as Invisible Bedrock. The Invisible Bedrock is the unbreakable void-like block that surrounds all four sides of the world. This block does not use the Bedrock texture.
 * The void fog doesn't shorten visibility when sunlight makes its way to Bedrock layer.
 * Going past the Bedrock barrier into The Void will cause you to lose 2 hearts approximately every half second once you reach below Y=-63, and will quickly kill you, even if you're on Peaceful. However, by hovering above this point using fly mode, you are able to move around underneath the world without injury, but no blocks can be placed under layer 0.
 * In maps generated before the Halloween Update, there were occasional gaps in the bottom layer of Bedrock that the player could fall through.
 * There are a total of 5 layers of Bedrock at the bottom of a world, from Y=0 to Y=4.
 * It is possible to get stuck in Bedrock layer if you don't have any blocks to help yourself get out.
 * Redstone was previously unable to be placed on Bedrock; this was changed sometime in Beta.
 * As of 1.0.0, Bedrock can be found by 5 different means: at the bottom of the Overworld, at the bottom of the nether, at the top of the nether, when an Ender Crystal is destroyed, or when the Ender Portal in The End spawns after the dragon is defeated.
 * In Classic, when you walk on Bedrock, it makes no sound. After if you walk on it for a while, and walk onto another block like stone or grass, the walking sound will rapidly play until you get off of the block or you wait for a while.
 * It is possible, but rare, for ore to be found encased in Bedrock.
 * Bedrock blocks are not affected by pistons. Neither is obsidian.
 * Bedrock is one of few blocks that can be found in all three dimensions (i.e. the Overworld, the Nether, and the End.)
 * On the Xbox 360 Edition, you cannot access the void, as the bottom layer of bedrock is unbreakable even in creative mode. However, layers above this can be broken.
 * In the Xbox 360 Edition, due to limited world size, the borders of the Nether are sealed with Bedrock. The final layer is unbreakable, just like in other worlds.