Minecraft Wiki:Issues

This page's purpose is to list all the bugs players have come across. They pertain to the unmodified, unhacked game. Most of the single-player bugs also apply to multi-player.

Version history also contains newer bugs that may not be listed on this page at the moment.

Bugs and feature requests can now be logged at Get Satisfaction: Mojang.

General

 * Whenever some Windows users lock their computers by either using "Start -> Lock " or a keyboard shortcut, and then log back in, the game window will be completely black. This can only be fixed by closing the engine or toggling the game between maximized and windowed settings.
 * Occasionally, the level.dat file is re-written, causing you to lose your held items, and generate a new spawn. This will in general corrupt both the level.dat and the level.dat_old file, and if you don’t have a backup or the back up is corrupt too and were using an automatically generated seed, the seed will be lost forever (this will cause strange terrain generation when you will explore new parts of the world).
 * Sometimes you can see through everything; this randomly happens on all games on all platforms. Toggling the fog distance will change everything back to normal (Default key is F).
 * ATI users with 6.x drivers will not be able to run the game at all.
 * Users with ATI x300/x600/x900 series graphics cards will not be able to play the game. It will freeze before the Mojang splash screen then display the "bad graphics card" error.
 * The renderer occasionally "conks out" leaving the user with the dirt background or a black screen. If the user has the dirt background and attempts to do anything, it will then give the user a black screen. If you tab out, or try to click or press keys, it will crash.
 * Some players exhibit lots of lag and crashes when trying to play the game.
 * When walking across the corners of holes under a ceiling that is only 2 blocks high, the player will fall 1 block and become stuck inside the block he was walking towards. The visual effect on SSP is that the player will slide towards the hole as intended, but on SMP the player will shake wildly - appearing to continuously fall off the edge - until the direction key is released.
 * Players stuck in walls (or whose lower-half is in solid block) will slide towards the nearest gap; however, if the player moves against this force, he will repeatedly slide to .21 and then walk back to .11. The player will not slide beyond .3 to be completely out of the wall.
 * Rarely, the game can think you are 1 block high when in water, and permits walking through water as if it was air. Your view will not be affected in both first and third person, but if you are in a one block deep water, the underwater screen shows and you may drown.
 * "Login failed" in Ubuntu. When several keyboard mappings are configured for the user, the username input uses the current mapping whereas the password input uses the default mapping, and leads to "Login failed" errors.
 * In the login fields,  or + does NOT let the user navigate between the "Username" and "Password" fields.
 * In Multiplayer, a player can see 2 players, one is moving and one is not moving, it happens when a player teleports to somebody suddenly, it makes lots of lag and then you will see another player from where the player teleported.
 * If you tab out without having a GUI open (Esc/Inv) it will act as if shift is held down when clicking on items.

Abandoned Mines

 * They can sometimes generate floating in cave systems (update: intended)

Audio

 * The openAL32.dll and openAL64.dll that come with Minecraft do not work properly. This sometimes causes Minecraft to crash when players turn sound on in the options menu. On Windows machines, deleting Minecraft's openAL files usually solves the problem, because Minecraft will then automatically use Windows operating system's copy of the OpenAL DLL, which works properly.
 * The audio position of the player lags behind where the player actually is. The supplied OpenAL DLLs lack 3D audio so it's hard to notice. However if you replace these DLLs with alternatives (such as the ones provided by the Creative drivers) you can notice that when you walk the footstep sounds are generated from where you were coming from, rather than directly underneath you. It is disputed whether this is a bug because it is not noticed with the provided DLLs, and 3D audio is something the game was not intended to support.
 * Saves might become corrupted when a Jukebox is activated with a Music Disc.

Terrain Generation

 * The "same chunk rotation bug" that has been solved in version 1.3 still exists for all caves in generated worlds. The solution to it should be similar to the terrain bug.
 * Also for caves there is a bug with an optimization, which causes the tunnel digging algorithm to stop too often, causing flat walls and cut tunnels at chunk borders here and there. Source code for fix has been made available.
 * A similar bug as the "same chunk rotation bug" that has been solved exists for biome terrain top layer block replacement algorithms. The chunks are not rotated, but the sand pattern and biome-based layer thickness values are calculated with mixed Y and Z coordinates, causing visible and invisible artifacts. Source code for fix has been made available.
 * Large sections of "floating blocks" have been generated on new worlds for some clients from a world in 1.5_01. The error only seems to appear in coastal areas in a large scale, floating blocks include: dirt, leaves and logs so far with select ores. Snow blocks seem also to appear on water.
 * As a result of creating lakes late in terrain generation, floating trees, sugarcane, cactus, and snow can occasionally be found floating above a lake.
 * Water and Lava lakes can be generated inside frozen oceans. Example.
 * There may be a hole in a dungeons floor, because a lava/water chamber may generate in the same place. If the hole will be under spawner or chest, this block disappears.

Lighting

 * There is a lighting bug in which levels below 32 are lit, causing immense lag when loading chunks. This effects the Sky Lands map and the Far Lands.
 * Smooth Lighting doesn't work when shadows are cast on water.
 * Smooth Lighting also doesn't work when light is cast on water.
 * Smooth Lighting acts weird on certain blocks.
 * On some systems, nighttime can appear excessively dark.
 * Blocks placed above snow-covered grass cause the lower blocks to appear darker than they should, but only with smooth lighting.
 * There exists an underwater lightning problem which is most likely located at chunk borders.
 * The top face of a button will appear darker when smooth lighting is on. This does not matter on what other lighting or blocks are near it.
 * Occasionally, some chunks of the map do not update with the day/night cycle,. Also, even in caves or closed environments the player can still see lighting bugs. These glitches are fairly common and can cause multiple problems. Usually waiting for a moment or toggling fog will fix this.
 * Some mobs will alternate between looking slightly darker, and normal "brightness", as they bob up and down while floating in water.
 * In 3rd person view, putting the camera in the water causes under water overlay not to show, making blocks light up.
 * In 3rd person view, when in water and camera is out of water the under water overlay is still on.

Stereoscopic 3D

 * Stereoscopic Minecraft has issues rendering chunks other than the one you spawned on and the ones directly around it.
 * Obsidian is too dark for the 3D to work at times.

Achievements and Statistics

 * The achievements "Time to Farm!" and "Time to Strike!" requires a wooden hoe and sword (respectively), despite the description not specifying and the player being able to build stone or better versions of these tools.
 * Throwing leather on the ground earns the achievement for killing a cow, thus getting leather.
 * The "Getting Wood" achievement is obtainable under any circumstance where a block of wood is collected, rather than only from destroying a block of wood.
 * Achievements saved when playing offline and achievements saved when logged into Minecraft.net are separate and do not sync.
 * Bucket usage is not recorded in the statistics.
 * The compass in the statistics screen will point toward the equivalent of the spawn in the Nether.
 * 1.7 appears to erase statistics and achievements at random.
 * Shears do not display a "Times Used" value under the items page.
 * Achievements and statistics are reset when Minecraft is shut down unexpectedly (e.g. due to a power outage).

Beds

 * You can break blocks while laying on a bed.
 * While sleeping, particles (torches, furnaces, etc.) do not "adjust" to face you, some of them may look flat or even be invisible.
 * Beds placed in fully enclosed areas (on both sides and with only one space above), or beds placed with no ground even with the block under the bed on either side (with only one space above), can cause you to wake up inside a wall, killing you and potentially destroying your items. This is due to player placement when you wake: if the game cannot place you on the ground level with the block below the bed on either the left or right side, it will place you on top of the bed. If there's only 1 block height above the bed, your head will become stuck in the ceiling, killing you.
 * Beds cannot be placed on snow.
 * Beds being broken appear to get brighter.
 * You can sleep while in a minecart or a boat. You still move with the minecart or boat but you may lose air when sleeping in a boat in water.
 * You can sleep during a thunderstorm, even during the day.
 * If you walk very far away from your bed and then die, you do not re-spawn at your bed and instead spawn at your original spawn point, receiving the message "Your home bed was missing or obstructed". This is probably due to the fact that the chunk has been unloaded.
 * If you break your bed while in it, you will wake up with an "oomph" sound and when you touch walls 2 blocks high, your screen changes texture and you take little damage, but if you touch a 1 block high wall you'll get pushed back as if you where pushing a mob.
 * Monsters spawn in your house if you go to sleep in a bed placed against the wall. This only works if the wall next to the bed is 1 block thick, and if the wall has ground level with the bed. Making the wall of your house 2 blocks thick or placing your bed where it is not against any walls will stop monsters from spawning inside.
 * Monsters spawn in your house if you go to sleep inside a room with a double-door that leads to the outside. This is caused by the second door placed being inverted, and the game thinks there is no door at all there. This can be fixed by having the inverted door open when going to sleep.
 * If a player tries to sleep in a bed next to one or more other beds in multiplayer, and someone is sleeping in one of the beds next to it, the player will often get the message "Bed is occupied".

Minecart

 * Powered Minecarts only push minecarts going north-south.
 * When interacting with a Minecart+Chest or Minecart+Furnace while holding a usable item (e.g. filled bucket, bow and arrow, food), the item will be used when the chest is opened (bucket emptied, bow fired, food eaten).
 * A player pushing multiple minecarts of any type can only push them going north-south. Attempts to push east-west only result in pushing the last minecart in the group, and sometimes no carts at all.
 * When closing or disconnecting from a server while sat in a minecart, on re-login you will be in a state of sitting but able to walk around until you sit back into the minecart you were in previously, this bug happens every time you load the game.
 * When travelling at high speed along a powered track (Ex. a track with booster rails every 10 meters) with render distance set to "far", the game may crash. When the game is resumed, Minecarts will spawn along the length of the track every five meters. This may be used to farm Minecarts at a large scale.

Chest

 * Both single and large chests can be opened when a transparent block is placed on top of them.
 * Both single and large chests ignore transparent blocks when choosing which way to display the front.

Crafting Table

 * Unlike other wooden blocks, axes aren't the most efficient tool to use to destroy crafting tables.

Doors

 * If you close a door on yourself and jump, you can stand on the lower half of the door. This can be used to climb on top of doors.
 * If you stand in an open door and close it, you are standing inside the door and can exit either way. It does not push you away.
 * When opening and closing a door, the sound it makes is randomly chosen between the open and close sounds, instead of specifically using the open sound for opening the door, and the closing sound for closing.
 * You can't place doors on glass or snow tiles.
 * The routine which determines whether you are sleeping in a safe place seems to ignore actual door state (open/closed). This is particularly important when your sleeping room has double doors to outside: as one of the doors is actually standing "sideways" and has default state (i.e. unpowered and not toggled manually) open for passing, you will not be able to have a successful sleep, monsters will spawn and raise you for midnight combat.

Farmland

 * Saplings can be planted on tilled soil, however they will never grow even when bone meal is used.

Fire

 * Fire (on Netherrack) spreads through walls, setting stone on fire.

Flint and Steel

 * If you attempt to light glass, farmland, cacti, ice, rails, redstone wire and similar things on fire, the durability of your flint and steel is lowered without any flames appearing. Sound of creating a fire is also played.
 * You can set TNT off with a flint and steel by simply left clicking it, using up no durability.

Furnaces

 * On destruction, furnaces may not drop a single item from the burn area.
 * When opened, lit furnaces are brighter than a furnace not open.
 * When opened, game crashes

Ice

 * Ice blocks do not have the slide effect on their border if no other ice block connects on them. Player will not slide even if the ice block is supporting him (i.e., the ice block borders air). Walking around in grayed-out area will not have the slide effect.
 * You can see chunk borders in ice, but only in Fast graphics.
 * Ice generation is based on the seed, not the terrain. If the terrain generation changes, the areas where ice will grow will change.
 * Non-level water surfaces directly under ice allow you to see underwater as if there was not any water there. The top of the flowing water does not render.
 * You can't see water through an ice block.
 * You can't see ice blocks through water.
 * Single blocks of ice that are melted via torch, glowstone, etc. do not flow. This is because the water/ice block does not update. Placing a block next to this water block will cause the water to flow.
 * When melting a block of ice by putting fire under it, the water will also not flow and thus not extinguish the fire. The player can then stand in the water and fire at the same time and will be able to drown and burn at the same time.

Interface

 * You are unable to directly swap items in your inventory if the two items are same. This is important if you would like to swap the same item type with two different durability values. This is a result of the way combining stacks works.
 * If a player enters a world, toggles debug mode (F3), then exits the world with debug mode still on, debug mode will still show.
 * If the player rides a vehicle and then opens their inventory, the player's hands will shift position in their view. This is most noticeable when the player has a map as their active item, and persists until the player opens their inventory again, even surviving reloads of the world.
 * Pressing a jump, movement, or sneak key at exactly the same time as opening the inventory will cause the action to be held. The inventory may then be closed, and the action will continue until the according key is pressed or the inventory is opened. Multiple keys may be "toggled" in this way. This trick can also be performed by clicking workbenches, furnaces, chests or dispensers.
 * Sometimes a jump or move key will get jammed and you will keep moving until you press the key that would normally make you jump or move that direction.
 * Opening the inventory while the player is sneaking will cause you to not able to click and drag items. Anything clicked will instantly be taken to or from hotbar. Survives world reloads and client reloads. This only applies if the user's sneak key is SHIFT.
 * When player touches a 2 blocks high pillar in 3rd person mode, the character's shadow displays on top of the pillar.
 * In the inventory the labels of the current window will overlap the currently moved items.
 * If you open your inventory while sitting in a vehicle and wearing armor pants, you will see that your legs will be bent in a sitting position but your armor pants will not. They will remain upright and come off your body right through your legs. The reverse happens if you put on armor while in a vehicle and leave it.

Lava

 * Sometimes, lava won't cause damage. More common in SMP.

Mobs

 * Creepers may spawn in open areas with torchlight.
 * Tamed Wolves will attack you if you shoot yourself with an arrow. This can be achieved by looking straight up, shooting an arrow, and moving forward a small bit to compensate for a small amount of curve. Another way is to shoot an arrow at the ceiling and stand directly under it and destroy the block the arrow is on. This will cause the arrow to drop and hit you.
 * Sometimes a tamed wolf may get stuck in the wall, causing it to suffocate. You can save them by breaking the block they are stuck in.
 * Mobs may emit their idle sounds in the moment they are dying. This sounds like a second mob is nearby, but is actually possibly not the case.
 * Skeletons' fired arrows originate from a block above their body.
 * If the player is chased by mobs and makes a lot of curves, a mob may move in a wrong direction for a very short time.
 * A wolf's muzzle slides in or out of its head depending on whether the wolf is looking left or right.
 * A cow's horns slide to the left or right of its head depending on whether it is looking left or right.
 * On SMP, if you are lagging, any monster that notices you and starts walking towards you, will not look directly at you right away.

Paintings

 * Paintings never use smooth lighting.
 * Light goes through paintings.
 * You can place paintings in signs.

Pistons

 * Pistons are not recognized as a redstone device, therefore redstone will not curve into them. Redstone placed underneath pistons will also not power the device. Instead redstone has to run straight into the piston.
 * Walking straight on to horizontal piston from head to container with a hole under container causes you to fall into the hole.
 * If a piston is extended, the player can walk right through the back/fall through the top.
 * Sticky pistons may not pull back the block when they are toggled on and off rapidly.
 * Glowstones that are currently being pushed by the pistons will not emit light, but the block will stay fully lit.
 * If a piston pushes a block that is on fire, the fire will be put out.
 * Pistons can be randomly powered even if nothing is attached to it.

Portals

 * Going through a portal causes really high amounts of memory allocations.
 * After entering a portal the distortion animation can appear even if the player hasn't moved but this will not teleport the player back.
 * Going through a portal while on fire will stop the fire animation when the player arrives at their destination, though the player is still on fire and will keep losing health. In single player the fire animation continues as normal.
 * When riding a Minecart/Boat/Pig into a portal causes you go get stuck in a block.

Redstone

 * The display of redstone wire differs from its behavior when it's placed beside a block with torch on top. Namely, the wire turns, connecting to the block, but doesn't actually power it.
 * Redstone is allowed to pass through transparent blocks, such as glass, slabs and stairs.

Repeater

 * Doors beside blocks powered by repeaters are not updated when the repeater changes state (forcing an update by placing a block updates the door).
 * Arrows momentarily detach each time a repeater changes state.
 * Walking over a repeater or trapdoor in a 2 block high space can cause the player to fall in the block below, allowing him to walk around in the block. The player can jump out the block at any time.
 * With the above effect, you can glitch through any block, including bedrock. (This mainly should be fixed for multiplayer reasons, as people can glitch into off-limit places.) Place down two repeaters, the first doesn't matter, and place down another repeater facing the same direction as the first, but one block behind and to the side. Then place a block so that the second repeater is behind it, and the first repeater is to the side of it. Then place a block 3 blocks above the ground, so there's only two block spaces below it. Place the block so that it's behind the first repeater, and to the left of the second one, and the first block should be in front and to the right of it. Walking in from the second repeater, going towards the first, will cause you to go through the block. To do this in SMP, you need to place a sand block on top of the first repeater as you walk into it. Video demonstrating the bug.

Rails

 * Water that flows onto a powered rail destroys the rail, instead of returning it to item form like it does for normal rails.
 * Rails can be powered without any redstone, as seen here, allowing players to create cheap, functional minecart tracks.
 * Powered rail fails to return to the unpowered state if a nearby block above it is powered, as seen here.
 * North/South oriented powered rails act as curved corner rails if it is powered and there is a track heading east from it.
 * Detector Rails with minecarts already ontop fail to ignite redstone when pushed over the redstone by a piston.

Score

 * When the player dies, their score is displayed as "&e0". This happens because a scoring system is yet to be setup in Minecraft and "&e" is supposed to be the color of the score number.

Seeds

 * In certain afflicted areas, placing seeds on two adjacent tilled dirt blocks will cause them to disappear, and drop a resource approximately the same percentage of the time if you had destroyed the freshly planted seeds with your hands. If you place one seed with no adjacent seeds on the afflicted area, it will disappear after a while.

Slabs

 * Wooden slabs use the same properties as stone. As in producing stone SFX and requires a pickaxe to mine.
 * Grass doesn't die under slabs.
 * If a slab is placed on ice, it still has the "slippery" effect.

Stairs

 * When climbing stairs, the camera shakes a lot more than when descending stairs.

Torches

 * The player can hit a torch placed on a wall directly behind because the hitbox is slightly larger that the closest distance the player can get to the wall. This bug occurs since Beta 1.6.
 * The smoke particles from a torch can move up through solid blocks; smoke from a torch immediately below a solid floor may be visible above the floor.
 * Can be placed on furnaces, crafting boxes, and chests when there is a glass floor in front of them, and the torch is placed on the glass.
 * Alternatively, this can be achieved by placing a torch on another torch as demonstrated in this video.

Water

 * Water currents do not push minecarts or activated TNT entities around.
 * Items which are detached by water (such as flowers, wheat, mushrooms, torches, redstone torches, redstone dust, and rails) will disappear and not drop a resource if water flows onto them directly downward.
 * It is possible to place water using a bucket in the space occupied by a detachable block or a ladder (but not a sign or slab) and the water will replace it without dropping a resource.

Weather

 * Clouds pass through solid blocks and can enter sealed off areas.
 * Rain or snow still occurs above clouds.

Mac OSX

 * Some Mac users have been reporting Minecraft crashing constantly. Setting the render distance to Tiny helps stop the crashing.
 * Cannot take a screenshot when the window is maximized.
 * Mac users cannot open up the "open texture pack folder." This causes a lot of trouble when a player would like to change his or her texture pack.
 * When closing the Minecraft window it can cause the computer to crash. This can be avoided be 'Force Quitting' Minecraft by using the keyboard shortcut: cmd, alt, esc or by clicking the apple logo then selecting the 'Force Quit' option.

Skins

 * If a player wears a helmet while his skin has a head accessory portion and he sneaks, the portion appears outside the helmet.

TNT

 * TNT is transparent. This bug was introduced between beta 1.5_01 and beta 1.6.4, and is present in beta 1.7.3.

General

 * Advanced OpenGL will sometimes clip visible areas, especially if you rapidly turn your mouse.
 * Sometimes blocks will fail to render, creating massive holes on the ground and walls, allowing the player to see caves and dungeons under the map.
 * On Linux, Minecraft loses its mouse focus on every click to X Window for a very short time. If a pressed key is released at this moment Minecraft won't register. This will cause the player to move even if the movement key isn't pressed anymore. This is due to a bug in LWJGL that was fixed in LWJGL 2.6. Replace Minecraft's copy with a newer version of LWJGL to fix this issue.
 * Sometimes mobs within a certain area will stop moving, and entering the area will cause the player to become rooted to the spot and often vibrate wildly. Many animations, such as digging and health recovery will be broken, and mobs that the player hits will constantly loop the damage animation without dying. It is not possible to catch fire. This is often called a 'bad chunk'. Even if the chunk is deleted and generated again the bug will persist.
 * Selection bounding box breaks ATI cards' anti-aliasing.
 * There's a file called map.txt in the achievement folder inside minecraft.jar that causes performance issues. Removing it may greatly increase your performance, but may reset your achievements.
 * Unable to take a screenshot in full screen mode on some computers.
 * Occasionally a block mined will not produce a resource block. This seems to be caused by putting the crosshairs too close to the junction of two blocks, causing the target to switch to the block not being mined. The block is destroyed, but the resource is not dropped.
 * When a block is mined, it will produce a resource block, but will not appear to be mined. This bug normally occurs when much of Minecraft's memory is being used up and can be fixed by restarting the game.
 * If a player drops an item, saves the game and returns, picks up the item, and closes the game without saving, the item will appear both in the player's inventory and on the ground, duplicating it.
 * If the game is closed without saving, recently added blocks will vanish, original removed blocks will re-appear and the materials the player used are not returned.
 * If Minecraft runs out of memory, it will show this error screen: Out-Of-Memory.png

Beds

 * If the player right-clicks the bed fast enough, they will receive a message saying This bed is occupied. This is caused by the last click to attempt to get in bed being performed during the game placing the player in bed, tricking the game into thinking someone is already there.
 * The player has the ability to destroy their own bed whilst in it during the fade, and as of 1.7 this allows them to take damage from walking into a wall, as the player's block collision is still disabled.
 * If the block on the pillow end of the bed is broken, the player will miss the bed and sleep on the floor when the player right-clicks on the bed.

Boats
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 * If you manage to stand on your boat while it is under water, the boat will be unable to rise. The boat will still retain horizontal movement, though, and will often slide out from underneath you.
 * If you save and reload while in a boat, you will no longer be in the boat.
 * Exiting a boat will sometimes cause the player to fall through it. This could be fixed by implementing code that would place the player one block higher than the boat when it's exited.
 * If an occupied boat crashes into an unoccupied one, only the occupied one breaks.
 * Parking a Boat on a half step port/dock (or Soul Sand) while riding causes damage to player. Sometimes full health is depleted to zero.
 * As of 1.6.6 you may crash a boat as hard as possible into land without it breaking while occupied, but as you exit the boat after a crash if the boat taps a solid block the boat will break.
 * Very rarely, when a world crashes, boats may appear along the path of an existing boat.

Furnaces

 * Furnaces emit light even if its face side is blocked. The block itself emits the light, rather than the front face
 * When you put coal and a smelting item in a furnace, then leave and re-enter the world, the fire icon glitches and will not shrink until the fuel source is about to run out.
 * The fire animation may not disappear even after the fuel is consumed.
 * After a use of a furnace, if there is unused fuel material inside the furnace, it will be invisible and burning animation is still played.

Glass

 * You can't suffocate while stuck in glass.
 * If you attempt to light glass on fire, the durability of your flint and steel is lowered without any flames appearing.
 * If a glass wall is placed next to TNT in water and you stand on the other side of the glass, you will always take only a half heart of damage.
 * Glass does not affect the orientation of chests and furnaces.

Grass

 * It appears that in arctic biomes, next to ice, grass can be generated underwater by the terrain generator.
 * Grass does not disappear if a transparent block (stairs, slabs or glass) is placed on top of the grass.

Gravel and Sand

 * Gravel or sand will not fall down if it is placed above a non-solid block, like a torch or flower. If blocks of gravel or sand fall onto a non-solid block, they will accumulate into resources.
 * If you break a block below gravel or sand and are walking into gravel or sand, you will literally walk into the gravel or sand.
 * If you allow sand or gravel to fall on you, after moving around it is possible to be in such a position that you will not suffocate and you will be able to see through the sand or gravel and any blocks connected to the sand or gravel. This can reveal caverns and empty spaces. (This doesn't really work as of Beta 1.6).
 * If you place a sand or gravel block then quit the game before it starts falling, upon reload, it will float. If a nearby block updates, it will fall.
 * When sand or gravel is generated above a cave (or any opening), it will float until a space by it is modified in any way.
 * In the Far Lands, sand and (mainly) gravel will fall in a weird way, and when they land on a block, they will (in some way) break and make pickup-entities, but still be there as a block. This is the main course of the massive lag, experienced in the Far Lands. However, it's unknown when the sand/gravel glitch actually happens, because it's first in the Far Lands, that such huge amounts of them spawns with air beneath them, allowing them to fall.

GUI

 * The debug menu may not be displayed properly when the GUI size is set to Auto.
 * Holding down or spamming right mouse button while holding down left mouse button will cause the "item action animation" to pause/stutter. The user is still able to mine, cut, etc. while the animation has paused.
 * When clicking the Back to game button, the click may "pass through" into the game, causing the player to unintentionally execute the left mouse button action.
 * When in third person mode, if the camera appears to be above the water but the player's head is in the water, the GUI will still be darkened.
 * It seems as though the fog button is reversed when in the caves. When its set to FAR its foggy. When its on TINY its clear. It works ok on the surface.

Ladder

 * Under certain conditions, if you are looking at a ladder, the selected block will toggle back and forth between the ladder.

Lava

 * Lava can sometimes fail to generate proper lighting into the surrounding area, and will not damage the player. These pools can be traversed one layer without injury - submerging into the lava will cause the player to take damage, as well as force relighting of the pit.

Maps

 * Sometimes while viewing a map the game will switch to a "saving chunks screen" then end on a black screen.
 * At times, the player's marker will spontaneously disappear.
 * Crafting a map underground and using it sometimes makes Minecraft crash.
 * When holding a map while breaking a block, the map clears and increments the map index to the next number. (map_0 to map_1, etc.)
 * If you take out a map while The Void is visible, Minecraft will crash.
 * Some maps in SMP will display normally while exploring, but once the user relogs vertical lines appear in the map that will not go away.
 * Sometimes maps will appear with the incorrect number on them, which can be fixed by dropping the map and picking it up again (sometimes more drops than just once).
 * Apparently right when you load a world - if you turn to the left you will encounter a 'deadspace' where your facing will stop as you continue turning past facing west (map-south). This will cause your facing arrow to 'lag' a few degrees resulting in an incorrect direction by one GUI 'tick'.  This 'deadspace' appears to save it's spot.  IE if you make 20 complete rotations to the left you can fix the GUI arrow by turning 360° 21 times to the right.  And likewise if you make 50 complete right turns, you will not encounter this bug unless you make 51 complete rotations to the left.

Minecarts

 * If a minecart is partially off of a sloped Powered Rail, in such a way that it does not move, and the player enters and leaves the cart, they may fall through the block beneath it.
 * In multiplayer (possibly singleplayer too) if a minecart travels a long circle (outside a player's render distance and back again) occasionally the minecart will become invisible and cannot be interacted with, but it will still interact with the world (activate detector rails etc.) All nearby invisible minecarts will become normal again after disconnecting and relogging to the server.
 * When minecarts are placed on a small circular track, they will gain momentum from colliding with each other.
 * Minecarts can go off tracks or crash through the ground if their momentum is too high.
 * If you start sneaking right after destroying a minecart, you may crash and get buried, but there is also a chance you will get multiple minecart drops.
 * When exiting Minecarts when there is a block in front, the user may rarely fall into the block beneath the cart.
 * If TNT is detonated near a minecart, it occasionally drops more than 1 minecart.
 * A player/mob can be in a burning minecart without taking damage or being set on fire themselves.
 * Water does not put out burning minecarts.
 * Minecarts will interact with blocks next to the track while turning. When a track turns to North or South and there is a block next to the turn track, a minecart will stop rather than make the turn. This does not seem to happen on turns going to East or West.
 * When a minecart goes around a U-turn at extreme speeds, the player's viewing angle may not spin around, and will rather stay facing forward.
 * If the player saves in a minecart, they will be ejected from it and multiple copies of it will appear, possibly getting stuck right next to each other so that they accelerate at high speeds. If this happens to minecarts with chests, the items inside the chests will be duplicated as well.
 * Riding a Minecart into a Nether portal will no longer crash the game, but will trap the player in the portal block. The player cannot exit the Minecart.
 * If you save and exit while riding a minecart then load the game, you will fall through the block below you and placed to the nearest open area, this may cause to loose hearths.
 * Getting in (untested getting out) of a minecart will cause the user to eat food (only tested with mushroom stew, not tested on multiplayer)

Mobs

 * If a mob is riding a minecart and 2 or more mine carts get stuck in each other, after destroying or moving the carts away from the other carts the mobs will be invisible.
 * When up close to any mob or player in the Nether, the inventory GUI will become much brighter.
 * Ghasts will shoot at the camera, not the player entity. This frequently causes fireballs to miss you in 1st person. The deviation is even larger in 3rd person view. This bug does not occur in multiplayer.
 * Mobs can move briefly before map data is loaded when signing out and loading the world, usually resulting in the mobs getting stuck.
 * If a wolf is tamed when it's attacking another mob, it may still attack it when on sitting animation.
 * If a Tamed Wolf is left sitting when you exit the game and you return to the game in offline mode, the wolf will not respond to the command to stand up and follow.
 * If you hit a pig with a saddle (by left-clicking) it will deal normal damage but it will also place the saddle on the pig.
 * If a creeper attempts to reach the character by running into a corner, and the block it is on is a ledge with no blocks on its level (or possibly above it), the creeper may stop as though it is hiding, then never move from that spot again unless the player breaks a block or moves the creeper to change these conditions. If the character moves to the other side, the creeper will randomly snap between staring at the player without moving and looking around as though it doesn't see the player. If the player gets close enough it will still explode.
 * If a block is placed directly above the water, and a wolf swims against it, it gets stuck and drowns unless the block is removed.
 * Tamed wolves or any other mob, whether friendly, neutral or hostile, will not avoid harmful blocks, such as cacti, fire, or lava.
 * When walking in a straight path for about 1500 blocks, the amount of of spawned mobs will start to stack up, not despawning. By the time the 1500 block distance is traveled, over 170 mobs will be spawned behind the player. This causes the area the player is in to stop spawning mobs entirely. (Confirmed in the Nether, unconfirmed in the Overworld.)

Mushrooms

 * Mushrooms can live and grow under direct sunlight under glass.

Nether

 * The lighting in the Nether can flicker in the distance as if in a thunderstorm if there is one raging in the over-world.
 * In the Nether corner Far Lands, About 3200000 X&Z, There will be a place where there is light, but no lava. (This is a part of the whole Far Lands "bug")
 * It is possible (although very unlikely) to have your main spawn point in the Nether the first time you go to a world. This means you can't get out of it without any hacks.

Paintings

 * Paintings can be placed inside snow.
 * If a painting is placed on a block with a fence on top, the painting may be 1x2 in size. This can not be removed without breaking the block or fence.

Pistons

 * When a piston pushes a block of sand towards a space with redstone dust on it, the game will crash and keeps saying saving chunks. This bug is nearly the same as the bug that has just been fixed where pistons couldn't push towards a space with redstone dust on it.
 * If 2 sticky pistons are placed on each other the bottom piston won't pull the top piston back down if the top one is still active.
 * If 2 sticky pistons are placed on each other with the top piston active and the redstone power (going) down, the bottom piston won't pull it's self in even if it's not a sticky piston.
 * If 2 sticky pistons are placed on each other with the top piston active and the redstone power on, the bottom piston won't activate at all.
 * If a sticky piston pushes a block of ice while in water, the arm of the piston will become invisible. video example
 * If you attempt to use a piston on a water source, the game will crash and keeps saying saving chunks.
 * Sticky pistons are only sticky while retracting. They lose their stickiness once fully retracted, thus a sticky piston pointing downwards can pull a sand or gravel block upwards, but the block will fall back down once the piston has fully retracted. This also means that a column of upwards-facing, extended sticky pistons that are deactivated in a top-to-bottom sequence will not result in a shorter column of retracted sticky pistons, but in a series of retracted sticky pistons every other block along the height of the column.
 * A player standing on top of a downward-facing, extended piston will fall through it when the piston is retracted.
 * Pistons powered from above can become stuck. See here.
 * If a piece of rail on a block with a button over a sticky piston and the button is pressed: the rail is pushed upward, the button is destroyed and the rail stays floating in midair over the block it was previously on.
 * If you have 4 pistons simultaneously pushing a boat or a boat with a person in it upwards, the boat (along with the player in it) will rise up normally. but if the person is standing on the boat instead of sitting in it as the pistons push upwards, the boat will stay where it is (inside the extended pistons) while the person will be pushed up. The boat will return to normal once the pistons are retracted. this bug applies with or without water.
 * Pistons can be powered from two spaces above. A powered block above an air block, which is above the piston will cause the piston to extend.

Portals

 * Being killed in the Nether will cause though you had teleported back from the location at which you died normally.
 * Dying while in the Nether will also ignore a changed spawn point (via sleeping).
 * If the game is closed while entering The Nether, you will be sent to your spawn point on earth without held items, as if you were killed. However, it ignores a when the player's spawnpoint is changed via sleeping.
 * If a player opens a work bench and putting items in it, while going into the portal(with water or something like this), the items falling down and they are verry buggy, but the most time it's able to multiple them, sometimes 1x, sometimes endless. Video demonstrating the bug.

Pressure Plates

 * Pressure plates (both wood and stone) have a tendency to fade to black when smooth lighting is on in some situations.

Rails

 * If a powered rail is placed directly adjacent to a slope and the power source is a lever hidden in a hole in the wall, riding over that rail will cause both the minecart and the player to be teleported into the hole in the wall, causing suffocation damage or death.
 * If a rail is powered by a button that is directly above the rail and there is redstone wire leading from the block right behind the button, pressing the button causes the rail to be powered until the rail is destroyed or redstone is connected to the rail.

Redstone Repeaters

 * Redstone Repeaters don't always toggle correctly; when a circuit is switched on, some repeaters stay off and vice versa.
 * Can happen multiple times over the same circuit.
 * More likely to happen over longer distances.
 * Removing the Repeater and then replacing it will put it into the proper state, but the problem can come back at any time.
 * Occasionally, when walking off of a redstone repeater in a room with a ceiling height of 2, you fall through the floor into the block down and next to the repeater.

Redstone

 * While destroying a block, quickly applying redstone repeatedly will cause you to see textures of different blocks. Also, quickly removing redstone AND attempting to mine the block it is on has a small chance to make it show the glitched grass texture on top of the block. More chance of this occurring on a dirt tile. This glitch is more common in SMP but can happen on SSP when encountering frame rates of less than 25.
 * There is a bug where redstone can be turned into obsidian using this device Not tested on Multiplayer.

Redstone Torches

 * Sometimes they don't return to on state until, server restart can fix it.

Sapling

 * A tree can grow on top of a player, suffocating them.
 * If a sapling grows in to a tree with a leaf block level with a slab it will be destroyed by leaf block and not become recoverable.
 * Birch and pine saplings will not grow adjacent to walls or other obstacles, like normal saplings will.
 * If a player is 2 blocks away from the sapling and uses bonemeal on it, the player will get stuck in the leaf blocks, able to move and not get hurt, like the leaf blocks are not even there. This only applies if the player is using Fancy graphics.

Sugar Cane

 * Bugs in the terrain generation code can cause Sugar Cane to float. This is a purely visual bug. You can see the selection box when you look at it, and changing nearby terrain makes it show up.

Snow

 * In snow biomes, water and lava lakes can generate below the snow and leave some of the snow floating. Players will fall through this floating snow.
 * Beds cannot be placed on snow.

Slabs

 * Skeletons and Zombies will not be set on fire in direct sunlight when walking on a slab.
 * When firing arrows at the opposite corner of the slab, your arrows may clip through and hit the block behind it.
 * When walking with 50-100% of your body over a slab, whilst being at the high of another block, the walking sound effect for the slab type will play, rather than the one which you are actually on.
 * A single slab cannot be made into a double slab if there is another solid block directly above the single slab. This is because Minecraft places the slab normally first, then realizes it's on top of another slab and combines them.
 * Torches, and other nonsolid items, can not be placed on single slabs.
 * It is impossible to be suffocated by single slabs.
 * With Smooth Lighting on, a slight amount of light can be seen passing through the sides of slabs. This does not affect mob spawning.
 * If a slab is placed on ice, it still has the "slippery" effect.
 * If half blocks are placed next to TNT, the damage is significantly reduced.
 * Neither single nor double slabs displace item entities.
 * When exiting and reentering the game while standing on a single slab with empty space below,you sometimes fall through the slab.
 * When putting a slab on a slab which has another slab below it (or more) all slabs combine into one double slabs block, thus losing one (or more) slab in the process. Also reproducible in 1.6.6 server.
 * If a sapling grows in to a tree with a leaf block level with the slabs they will be destroyed by leaf block and not become recoverable.
 * When wooden slabs are mined, the stone mining sound is played.
 * If a single slab is placed on a lower block and another single slab is placed next to but one block up from the lower slab, and the player attempts to walk diagonally across the lower slab and towards the higher one, there is a chance that the player may no-clip through the higher slab and fall through it. Example: video of the bug

Tools

 * Axes do not break certain wooden blocks faster than hands, like you would expect. These blocks include wooden stairs, fences, wooden doors, signs, crafting tables and jukeboxes.
 * Using a hoe on a leaf block does not degrade the hoe's durability, nor break it faster.



Water

 * Water sometimes doesn't flow into newly generated areas (usually when a cavern is being generated near a body of water).
 * Unlike Glass, other water blocks are invisible when viewed through a waterfall, even though there is air in between.
 * Water source blocks do not regenerate over non-solid blocks such as glass or other water.
 * When opening your inventory when swimming, you can only move left or right until you move.
 * Upon entering a newly generated map, water may be found floating in midair.
 * Water lakes will not freeze automatically at map generation.
 * When in third person and underwater, the view will be darkened even if the apparent camera position is above water. And vice versa (you being above water, camera being below).

Weather

 * When lightning strikes, ice, water, portals, rain, snow, and other particles behind it become see through.
 * When rain puts out a fire on Advanced OpenGL the area will sometimes stay lit.
 * Sometimes rain and snow both fall at the same time in the same biome.
 * Rain and snow fall above the cloud layer.
 * Rain does not pass through signs.
 * Rain can't be heard over layer 95, which is under the cloud layer.
 * If you save during rain and load later, you won't hear the rain's ambience sound.
 * On "Fast" graphics setting, rain still creates particles on contact with the ground, causing slowdown on computers that can't handle it.

Mac OS X

 * On some Mac OS X Systems, the World Select screen will not appear at all, making the game unplayable on those Mac systems.
 * In other cases, the Mojang AB logo will appear green and the title screen and the game in dark areas will appear red.
 * Since version 1.3, on some Mac OS X systems, when the player closes the game (clicks the X button on the window) the computer will freeze up completely. The mouse will still move, but nothing else responds, forcing a hard shut down and restart. In addition, the system does not acknowledge the issue (e.g., no crash report window, no system.log entries). When on an afflicted computer, this rarely may not happen (often after a reboot or game update).
 * Afflicted systems seem to be older 32-bit Intel Macbook models, such as those made in and around 2007.
 * A work-around is to save to the title screen, and then Force-Quit Minecraft, instead of properly closing it.
 * It appears to only affect users with Intel GMA 950 graphics processors, known for its incompatibilities with 3D games.
 * Under MacOS X, Minecraft does not respond to either the Quit item in the Minecraft menu or it's shortcut, ⌘Q. This can be fixed by closing the window, then quitting Minecraft.
 * Pausing the game and expanding the window (+) as soon as the map is loaded causes a kernel panic, forcing you to restart the computer.
 * The game runs slow on Mac OS X 10.6 using a NVidia GeForce 320M graphics chip (it has some lags getting more and more as you play), however it runs with 60 or more FPS (average 120) on Ubuntu, using the same system. (Driver support fail) This bug isn't fixed with Mac OS X 10.6.8, though it includes new graphics drivers.
 * Minecraft uses an 8-bit depth buffer on many macs, including brand-new high-end ones. This makes distant objects look terrible! It can be remedied by specifying the size of the depth buffer when creating the PixelFormat for the OpenGL context. Changing Display.create to Display.create(new PixelFormat.withDepthBits(32)) in net.minecraft.client.Minecraft.startGame fixes the problem. Look at this before and after screenshot and notice the huge difference.
 * On some Macs, there is no audio, when you turn on the sound on Minecraft, the game hangs for a minute, then returns to normal, but still no audio. Otherwise, try holding F3 then press S while you are in Minecraft.
 * Since a recent update (roughly on 5/1/2011) to MacBook Pros (2011 model), there are patches of white in the sky on many users clients. Additionally, the health bars of items are white and the background to the inventory and options menus are completely white. Also, when you sleep it becomes all white as well. Force updating the client does nothing to help nor does updating your Java.
 * One user noted that after removing the Minecraft folder in /Users/nickname/Library/Application Support the problem is fixed until you change something in the gfx settings of Minecraft (turning on OpenGL). After you change the settings the only way to fix it back is to remove the folder again (manually switching to the default settings doesn't fix it)
 * Another user noted that it can be fixed by turning off Advanced OpenGL and then restarting Minecraft. However, the problem returns when the user turns Advanced OpenGL back on. Since the game performs better with Advanced OpenGL on, users still consider this a bug.
 * After researching the bug, one user found that many of the effects of the bugs are from Intel's poor driver development for the Intel HD 3000 GPU. This GPU is only used in the Macbook Pro 2011 13" model and thus the reason for the glitches.  As for the fix, after  speaking with Intel they said that Apple develops the drivers for their Mac GPU's and not Intel themselves.  As of 7/21/2011 this bug still exists.  However, it seems that with the release of Lion OS X, the drivers might have been developed more.  According to the change log of the OS, no further release of an Intel driver is mentioned, however on Minecraft with OpenGL turned on, it works fine, EXCEPT that it has created new glitches! In one users inventory, the sides of blocks are blacked out and so are the sides of animals at random.
 * Sometimes while trying to close the Minecraft Client in Mac OS X with the X button, it will freeze up for a few moments, while you can still move your mouse around and click, the X button will freeze, then allow you to click it again.

General

 * If a player has respawned, he can place blocks on the block he is currently standing on. This will not decrease the block count in his inventory, effectively cloning blocks. This bug only occurs with non-opped players.
 * Full server world saves do not reliably save the entire world. This can be proven on a single person private server with whitelisting enabled when attempting to do a full server save via:
 * 1) Disabling incremental level saving with 'save-off' on on Minecraft console.
 * 2) Forcing a full save to disk with 'save-all' on on Minecraft console.
 * 3) Archiving and saving the archived world with 'tar -xvzf save.tg world' or '7z a backup.7z worldfolder/' on shell in secondary system console.
 * 4) Turning back on incremental level saving by doing a 'save-on' on Minecraft console.
 * Enormous, cuboid areas (usually one or two chunks) of unfinished map open in random places. Caves, minerals, water, lava and mobs are visible when a Player peers into one of these voids. These areas cannot be walked on, causing a "[user] moved wrongly!" message to appear in the Server; however, players can ride minecarts through them with relative ease. Players can, however, walk "into" one of these voids (if it appears in front of him/her) resulting in the player falling repeatedly until the map renders itself. If the void appears in the middle of water, Players can "float" over the void using a boat. Placing a torch next to one of these "void holes", dumping lava or water nearby, or disconnecting and reconnecting to the server will make the land inside of them reappear. These have become significantly less common since the 1.3 update.
 * Occasionally, the level.dat file is re-written, causing Minecraft to generate a new spawn. Also occurs in SSP.
 * Upon being teleported with /tp, chunks will load in order from closest to farthest from the point the player has been teleported from. This results in the world appearing very slowly and glitchy for a while, especially on slower servers.
 * If a player stands one block down and to the side from a portal and uses a crafting bench, putting an item into the 3*3 crafting square, they can then wait for between a minute and two minutes, and the portal will bring them to the Nether despite the fact that they are not technically in the portal. This causes the item in the crafting square to duplicate, as well as possibly turning it into a very glitchy item which, after dropped, can be picked up any number of times, appearing in the player's inventory but not disappearing from the ground.
 * Ambience sounds do not play in SMP.
 * The world data and the inventory of a player are not saved synchronously. If a player puts an item in a chest and the server crashes, the item will be both in the chest and the inventory of the player (duplicated).
 * Some players have issues where they can send information to a server fine, but have large amounts of lag when receiving information from the server. This results in SMP being unplayable for players who experience this bug.
 * Sometimes the client is slightly off on the position of other players, causing them to consistently appear slightly off of their actual position. This can cause players to appear to be inside floors or walls.
 * When collecting a block/item on the ground, the icon in the inventory's hotbar does not distort for a short time.
 * Thrown snowballs, eggs and fishing rods have no effect on players, only on mobs.
 * Sometimes when connecting to an SMP server, an 'End of stream' message appears. After this message appears, the Minecraft client may need to be restarted or left alone for roughly 5 to 10 minutes before it will work.
 * Notably with Sand, the sand may continue to hover in the air after being mined out and continue to bob up and down. Placing a block in the spot does NOT override this.
 * Also, blocks mined on the edge may continue to show the dropped block animation falling repeatedly. Retrieving the block at the top of this cycle will allow one to pick up the block
 * Occasionally players will become invisible to each other at random times for no particular reason and will subsequently reappear just as randomly. Players may still interact with each other (damaging each other, mining terrain, etc.) but will be invisible. An entertaining video example
 * If you disconnect while you are falling, you will not take fall damage, after you reconnect. The same applies for any form of damage. This is due to the 3 second invincibility period after respawning/logging in.
 * When connecting to a server, the player's disconnect position may be changed or rounded. This can result in the player position moving vertically to the closest 1x1x2 open space directly above the rounded coordinates.
 * Deaths or Player kills are not recorded in the statistics when the player dies.
 * People are sometimes unable to talk on chat in every single server.
 * Blocks regenerate during a lag, so players can suffocate in them.
 * Server incorrectly reports "Failed to load ip ban list" when started with a missing ops.txt file.

Achievements

 * Some Achievements may not show up when you get them.

Arrows

 * A heavy arrow deathmatch causes severe lag on the server, takes minutes to recover. (picking up the arrows helps)

Beds

 * Sometimes when a player is sleeping and other player walks on that sleeping player the sleeping player will fall through the bed and the floor.
 * Trying to get into bed while sneaking disconnects the player(Illegal Stance).
 * If someone uses their bed in SMP, other players may get disconnected(Unrecognizable Packet ID: 17).
 * Attempting to hoe under a bed that would experience the monster spawning error would kick the player that used the hoe (illegal stance).
 * When right-clicking on a bed constantly before it is nightfall, the server may register that the player enters the bed, while the client believes the player is still not in the bed, causing the error message, "This bed is occupied," even when it appears there is no player inside. Other players will see the affected player moving around while he is in a sleeping pose.
 * The above "this bed is occupied" glitch sometimes also seems to occur if a player tries to enter a bed mid-jump.
 * If you try sleeping in a bed on SMP server while standing on it, it will start giving message "This bed is occupied" and you will be allowed to freely walk, but you will be really sleeping. Players will see you move but you will be lying down. You cannot trigger pressure plates while "sleepwalking", nor pick up items.
 * A right-hinged door (when looking from the outside) will act as though there is no door present and as a result, you will be attacked while trying to go to sleep.
 * When a player goes to sleep in bed between the trunks, it is shifted.
 * In some cases, even when there is a block protection on a bed, you are still able to destroy someone's bed by first destroying the lower part, and after that the upper part. Please note that this is not the case on some servers, because of 0% lag.
 * In SMP if you sleep in a bed someone else placed, a monster will spawn next to the bed of any one random person who is in bed, including but not necessarily, you. This can be fixed by breaking and replacing the bed.

Boats

 * If you ride a boat over a chunk of water which did not load properly ( ex. the water is really there, but you can't see it and can see through the whole world ), the boat disappears.
 * Standing on a boat causes jittering of the player, similar to the old fence bug.
 * When a Boat gets damaged (by a player), it does not shake.
 * If you see a player riding in a boat, it sometimes looks like they are running in the boat, rather than sitting.
 * If you exit a boat, you may get stuck standing on top of the boat, constantly falling and being reset by the server. This is similar to how fences used to act. You can get off the boat by getting out while it is moving, as the boat will slide out from under you and eventually allow you to fall into the water.
 * This may kick you from the server with message "flying not allowed"
 * The boat turns in intervals of about 10-20 degrees, making turning extremely difficult in tight spaces. In between intervals of turning, holding left or right will cause the boat to strafe left or right, respectively.

Cactus

 * 1 block high cacti do not always appear, causing invisible blocks of pain. The outline of the cacti cannot be seen, so it is not a rendering issue. Destroying the block underneath the cactus causes the cactus to drop. Disconnecting and reconnecting forces the cactus to appear.

Compass

 * When spawning or crafting a compass in SMP it does not take you to your spawn, it creates a totally different 'north'.

Detector Rail

 * When placed immediately next to a track switch, will crash the server.

Fire

 * If a player touchs fire in a server where damage is toggled off, the character will burn without taking damage. Notch has yet to say if this is on purpose or not.

Furnaces

 * Furnaces stop smelting items during a severe lag.
 * Furnaces occasionally turn to another direction after being placed. Appears to be random.

Jukeboxes

 * Setting a jukebox on fire when it is playing a disc may cause the game to crash.

Lightning

 * If lightning strikes a painting, it causes a server exception and crashes the server. (Caused by net.minecraft.server.EntityPainting.damageEntity)

Maps

 * When multiple players are using the same map, the orientation of the arrow only represents the direction the current user is looking, not the player the arrow is representing. When the user of the map rotates, all the arrows rotate.
 * When the server's view distance is set to a lower number (5) walking with a map may cause the server to lock up . Setting the view distance back to the default of 10 fixes this.
 * If a player moves too quickly horizontally while holding a map (usually from flying or teleporting), chunks will stop loading for that player and possibly other players, eventually kicking them off of the server due to timing out. The kicked players will not be able to log back into the server until it's restarted, despite there being no such problem for other players.
 * Some users have reported their maps becoming glitched and do not display properly if they relog with the map in their inventory. Giving the map to another player and having them give it back or putting the map in a chest and taking it out again seems to fix this until they log off again.

Minecarts

 * Engines consume coal but do not move under their own power, making them useless.
 * Empty/Storage Minecarts start to behave strangely when they are too far away from the Player. They disappear completely, disappear until Players disconnect and reconnect, or suddenly stop on tracks despite having sufficient momentum.
 * Minecarts load before terrain sometimes causing them to be invisible until they are interacted with. Large transit systems and door water boosters are examples of when the issue occurs. (log out/in to reproduce).
 * Minecarts being destroyed do not wobble.
 * When you're trying to send a Powered Minecart to a destination that is far away, the minecart stops after a while and never reaches its destination. But if you approach the powered minecart, you can see it moving again : you have to stay close to it.
 * An unpowered Powered Rail does not stop or even appear to slow down a Minecart when it is travelling very fast.
 * Three unpowered pieces in a row seems to stop it every time but frequently on the last piece.
 * If a mob spawns on a powered track circuit it will be pushed around it.
 * Stacked Minecarts glitch out and jump up and down.
 * An empty minecart too far from a player on powered rail will come back, when it would stop at the end had a player been with it.
 * A minecart ridden off a jump damages the ridder just as they leave the jump, not when they land. (witnessed after full boosting by a powered track)
 * An empty minecart falling more than 3 blocks (enough to deal damage were a player riding in it) and landing on tracks will cause any subsequent rider of that cart to take damage when any fall occurs, regardless of height. If the cart is removed and replaced on the tracks, the damage does not occur. Easily reproduced by placing a minecart on a powered downhill rail 5-6 blocks above a loop-track with a 3-block fall. Sitting in a cart on the 3-block fall track normally causes no damage, but starting the cart on the powered rail at 5-6 blocks, landing it on the 3-block fall loop, and getting into the cart and starting the loop will cause damage on the 3-block fall.

Mobs, Hostile

 * Shooting animations (Ghast fireballs/opening mouth and eyes, Skeleton arrows) are not always visible. The sound of these actions (Ghast scream and Skeleton "twang") cannot be heard either.
 * Ghasts' fireballs occasionally do not explode, only lighting a small area on fire.
 * Sometimes mobs freeze in animation and can not be hit. They disappear after about 2 minutes. They are client-sided, so no other players will see them.
 * Some users are reporting mobs will be invisible, but can still attack you. On update 11/24/2010 Notch explained that to see invisible mobs, players must set their difficulty to the server side difficulty or higher.
 * Sometimes when the character dies, monsters will stay loaded client-side and not be loaded on the server side.
 * Sometimes players can hit mobs multiple times before the server registers the hit. The hits will then all register at once and the mob will be subjected to several knockbacks at once, flying into the air.
 * When a mob dies, its corpse sometimes is still visible in the red death animation and vibrates.
 * The lower half of mobs can not be hit with a melee weapon when you are 1-2 blocks below them. They can, however, be hit from directly underneath.
 * When a mob chases the player, it does not look directly at the player. This is caused by server lag.
 * Hostile Mobs can hit you from farther than normal due to normal server lag.

Mobs

 * Sometimes, Mobs of all types sink of 1 blocks in the ground, resulting in almost invisible mobs and darker mobs.
 * Sometimes mobs take no damage falling into running water less than one block deep, even if the player takes over 10 damage falling the same distance into the same water.
 * Mob spawn rate seems significantly lessened when server view-distance is under 10, possibly related to mobs seeming not to despawn from chunks unloaded earlier than usual due to the setting. Set view-distance back to 10 (default) for proper behavior.
 * Mob spawners always show a pig rather than the mob they actually spawn.
 * If a mob spawner is placed on grass, it will spawn client-side ghost pigs that cannot be killed.

Mobs, Passive

 * Squids can fly upwards.
 * Squid moving on the bottom of a body of water make the normal "footstep" sound.
 * Occasionally after dyeing a sheep they will still yield wool in their original color (i.e. white).

Mobs, Friendly

 * Occasionally, Wolves can disappear on SMP Servers, Disconnecting and Reconnecting fixes this.
 * Sometimes after reconnecting to a server, wolves that were previously sitting will appear to be standing. They will still behave as though they are sitting.
 * Occasionally when wandering a significant distance from a sitting wolf, it to teleport to your location and become active.
 * Sometimes after you go to sleep or are away for a while, your wolves will appear standing, although they act as they are sitting. This happens in both SMP and SSP.
 * After the 1.6 update, some tamed wolves will act as wild wolves, They don't to stand up and attack you after you hit them.

Nether

 * The Nether and Overworld Merging together in chunk spawning. nethersmpglitch.png

Note Block

 * Note blocks and especially note-block-combos tend to react really easily on server's lag. Unable to make any longer noises / songs with note blocks on multiplayer.

Paintings

 * When copying an SSP world onto an SMP server, paintings are removed in the transition.
 * Paintings can be destroyed in spawn-protected areas.

Pistons

 * When Redstone (dust) is placed on a block behind a Piston and activate the piston does not respond - as expected. Removing the piston then replacing it in the same spot will then activate it. It may be easier to watch this video example
 * Items ejected when a piston pushes a block in their place cannot be picked up.
 * When pulling an Ice block with a sticky piston it cases the water to 'leak out' pushing it back then stops the water and causes the piston head to become invisible. (Still existing in 1.7.3 after the 'fix') video examplesecond example
 * When two pistons (one sticky and one regular) are used at right-angles to each-other a block deletion/disposal glitch is created. This also reacts strangely to Ice blocks. video example

Portal

 * As of 1.6.X, there is a chance of Minecraft's renderer to stop functioning (you can hear the audio going normally, and the server still registers you as playing), leaving you with a black screen, when you use a portal in SMP. Rejoining the server fixes this, but is a workaround.
 * When a portal is placed along the edge of a chunk (for example, the entire portal is along the x:-31.5 coordinate), and is used as a DESTINATION portal (as in, it is the portal you're teleporting TO) you will frequently find yourself "falling" before the chunk loads, and will actually end up "stuck" buried up to your waist in the obsidian base of the portal. This results in you being "stuck", bouncing up and down. You can usually free yourself with much struggling and jumping, but it's difficult. (Verified on a 1.6.6 unmodified server, with no client-side mods. - Moleculor 02:05, 13 June 2011 (UTC))

Powered Rails

 * When riding uphill in a minecart on powered tracks at full velocity, the cart will turn back.

Redstone

 * As of Beta 1.6, the maximum size of a Redstone circuit is limited by the new server option view-distance, which makes HUGE circuits unable to work, except other players keep necessary chunks active.
 * Since Beta 1.4, pulsars do not work, and many circuits have become glitchy in SMP.
 * Sometimes after waiting long enough (10–20 minutes?) a pulsar will start to work.
 * Giving redstone torches short pulses (via edge detection) causes them burn out, even if there is a pause > 5s between pulses.
 * As well as repeaters, torches lock their state randomly when being wired for clock generating.
 * While destroying a block, quickly applying redstone repeatedly will cause you to see textures of different blocks. Also, quickly removing redstone AND attempting to mine the block it is on has a small chance to make it show the glitched grass texture on top of the block. More chance of this occurring on a dirt tile ( unconfirmed ).
 * Redstone Repeaters occasionally become locked if their chunk becomes inactive while they are in their "on" state.
 * Occasionally Redstone does not properly turn on/off when you remove/add the block powering it.
 * Redstone torches will sometimes disappear if attached to the side of a block that is in a different chunk (to the east or west) than the torch. They may also disappear under other conditions.
 * When creating double-doors, you need to make an inverter and sometimes the inverter stays in the state that keeps the door closed.
 * Sometimes when walking over redstone wire you fall through the block.
 * Setting the time using /time set will occasionally lock repeaters (1.7.2 tested)
 * Blocks will occasionally enter a state in which torch placed into that block in any orientation will not relight. This is related to the use of /time set. Rebooting the server seems to fix the issue until it occurs again. (A fix would most likely fix many of the bugs in this section.)

Signs

 * When a sign is placed in multiplayer and text is entered (but not finalized), and a torch is placed within 10 blocks of the player who placed the sign (not the sign, but the player), the entered text disappears. Interestingly, when a torch is placed within 10 blocks of the sign placing player BEFORE the sign is placed, any subsequent text entered will not be erased by torches placed OUTSIDE the radius of the first torch, but text will be erased by torches placed INSIDE the radius of the first torch. Oddly, this behavior only seems to occur with torches, though these tests were not exhaustive of the minecraft block set, and further work should be done to verify this claim.
 * Similar to the above effect, "active" sign text is reset if a cobblestone block behind and to the left of a sign is mined out and regenerated by a cobblestone generator.
 * Changing redstone charge also does this.
 * Pistons also cause this to happen (but that might be because redstone is triggering them) - possibly the update of the surrounding area by anything other than a player's placing/removing causes the dialog to reset (the game replaces it because its block was updated?).

Time

 * The server command /time breaks 'clock based' circuits. Using a bed to change time does not affect the clock generators. Restarting the server fixes circuits until the /time command is used again.
 * When the /time command is used by 2 people at the same time, the time may not change at all, it suddenly can become dark, no matter what value is entered, or the server lags so much it needs a restart. This mostly happens on Hamachi/slower servers.

TNT

 * A TNT block meant to drop will enter a repeating fall animation (but not actually fall) when lit.
 * If a lot of TNT is lit, some TNT may explode but leave behind an image of an exploding TNT block that is almost completely white, and will hover in mid-air while repeating the falling animation. The ghost TNT will not disappear unless the player disconnects and reconnects. (This is a client-side TNT entity)
 * The explosion result differs between clients for ~5 seconds, but as soon as the chunks update, the server-side calculated explosion will be shown.
 * You cannot use the pushing force of TNT to jump higher in SMP.
 * TNT doesn't make the fuse sound in SMP when activated.

Trees

 * Trees that have grown recently, especially packed together in a tree farm, sometimes don't update the client with the leaf positions. This creates "invisible" leaves that the player can't walk through and makes navigating tree farms an annoyance.
 * Using bone meal to quick-grow trees will sometimes cause "floating" trees to grow with the sapling still at the base. Removing the sapling or using more bone meal can cause the tree to grow into an enormous bundle of leaves with no log base. These leaves will now respawn immediately after being harvested. The only way to remove these glitched leaf blocks is to burn each block individually (fire will not spread for some reason) OR set the floor below the leaves on fire OR build an umbrella above it, the shadow seems to instantly vanquish the leaves. - This glitch is vastly more common when quick-growing trees under another trees foliage. Again, disconnecting and reconnecting will reset these "ghost trees."
 * Planting a sapling and waiting a bit will sometimes yield tree trunks with weird distributions of leaves, and in some cases, no leaves at all. Trees can also grow but be invisible, making it impossible to traverse a tree farm after a while. Rejoining the server appears to make invisible trees visible again and fire will swiftly cause phantom foliage to be made manifest. You can also place a torch to make the phantom foliage appear.
 * Leaves from trees will overwrite some blocks, such as a nearby fence. This is problematic when it renders areas previously thought safe accessible to hostile mobs.
 * Birch saplings will not grow in underground tree farms, even though there is proper lighting.

Tools

 * The last use of any tool causes a block to not drop, unless you normally get a drop from using your hands, bug first reported from before 1.2_01 in both SP and SMP, and last reproduced in SMP 1.7.3.

Water

 * Client and server breath meters are not synchronized. This sometimes causes the client to register the player has gotten air, but the server to start drowning early.
 * In some underwater areas there are lines of lighter spots at the bottom the water, likely on the edge of chunks where the next chunk over used to be empty space (causing light from the side to reach the bottom on the edge of the chunk).