Known Bugs And Glitches

''This is a list of Bugs and Glitches currently in-game. If you find a bug, please list it below to allow others to see.''

''Keep in mind though, just because a bug can be exploited doesn't mean you should. You need to play the game the way it is most fun for you. Duplicating items may seem like a good thing to do at first, but it can rapidly make the game a lot less fun to play.''

General

 * For all those playing with a pre-1.1 character then you may notice that your maximum mana is 260, not 200.
 * The item value has no space between for example Gold and Silver coins.
 * Creating a single player world can crash the game and delete everything you have gotten on that character in a while.
 * The Hermes Boots or Spectre Boots can let you fall through gaps in the floor one square wide if you run into a wall just above it fast enough. The Hermes Boots can also let you go up 1 space holes while running and jumping (Rocket Boots recommended).
 * In single player only, it is possible to drink an unlimited number of potions without activating the Potion Sickness debuff. To achieve this, you should first have autopause on. Swing any weapon or tool and pause the game right in the middle of the swing, a feat that is easier to do with weapons that swing slower. Afterward, select the healing item by left-clicking or right-clicking the item of your choice. Unpause the game and your character will interrupt the swing and instead consume the healing item. It is advised to use right-click, because left-clicking will select the item stack and throw it out immediately after drinking. There is a possibility where you might "eat" items this way where certain items are consumed when you pause the game and accidentally select an item with a different intention while swinging.
 * Placing two doors adjacent to one another and repeatedly opening and shutting them may lead to one of the two doors glitching, which results in spawning an infinite number of duplicate doors whenever the adjacent door opens or closes. Though extremely tedious, it is possible to exploit this glitch to earn significant amounts of gold, as each stack of 99 doors is worth nearly 40 silver.
 * Fall damage is inconsistent when landing on anything 1 block (sometimes more) thick.
 * It is possible to use the Grappling Hook or its variants to go through tight spaces you can't normally get through. This can kill you if you try to do it near sand.
 * Sometimes if a player joins a multiplayer server, the menu music may still play while the in-game music is playing. It may or may not be related to the issue where day and night music play at the same time.(Day, night, and title could also all be heard at once.)
 * Occasionally, clicking the GUI opened for a sign can cause the game to crash and pull up a .NET error message.
 * Sometimes if you are playing in Multiplayer and you place more than one gold key in a chest, it duplicates and becomes 99 gold keys.Floatingpbank.jpg
 * Chests will float if the sand they were place on is removed, though not from directly under it. The sand must fall by removing the tiles below it.
 * While playing on Multiplayer or Singleplayer, aGold_Chest_spawned_on_Platform_bug.jpg glitch may occur that will allow the player to walk inside of a door. 1 player must be very close to the door, and have good hand-eye coordination to be able to move quickly as the game changes. The 2nd player shall open the door the 1st player is close to, then close it very quickly. If done correctly, the 1st player will be stuck inside a door, and be able to move freely through it. If the door is opened or destroyed, this glitch will wear off. (Can be done in singleplayer without the help of anyone close the door, move as close as possible to the door, open it, tap your move right key once very quickly, close the door, move farther into the door. you should not notice even a pixel's worth of movement if you do this correctly.) [Can also be achieved if you use the active/inactive stone blocks, and a switch. stand in the blocks, flick the switch (Note: switch must be connected to the blocks via wire) and you will be able to move around in the blocks] It is also possible to do this by having a mob hit a pressure plate when you are standing in the spot the door will end up in.
 * When you kill yourself smashing a Demon Altar, there won't be a 'death message', just your character's name.
 * Aside from the bug with the death smashing a Demon Altar, sometimes you'll die and not see a death message, just your name, without doing anything particular or dying because of a certain thing.
 * When there is a Chest surrounded by thorns, break the chest, then start with the thorns. Every few thorns will spawn four collectable chests.
 * In multiplayer, if the server is laggy enough, once you fall down, say, a Hellevator, the map will not be loaded. You might hit the end of the world without touching any bricks and will need to dig yourself out, or use a Magic Mirror.
 * If you place a bottle on a wooden platform and place a torch next to it, the torch will break and some torch particles will appear.
 * As of 1.1, all four edges of the world were moved closer to the spawn point by at least 12 blocks, making anything built along those edges in-retrievable. If your bed was in that area, you spawn on the nearest block to your lost bed on the new edge of the world. Sometimes in multiplayer, when a world is updated to 1.1, 12 blocks on each corner will be removed, but the size of the world will remain the same, making a 12 block wide/high space that contains nothing that the player can access. The map generator was not updated to handle this, and Golden Chests at the edge of the world in the Oceans will not be visible. This bug can easily be solved using F9 to cycle through your light engines, two of which cause this 'shrinking' of the map.
 * If you die while fighting the Frost Legion, you will drop coins like with any other mobs. However if you drop platinum coins they may not show back up in your inventory, or the name may show up in the slot, but no coin is actually visible. Where they should be in your coin count you can right click and hear an audible "click" like there should be an item there however you cannot interact with the coin, and NPCs (i.e. the Shopkeeper) won't acknowledge you actually have the coin.
 * Occasionally, when leaving and then proceeding to join the server, you may get a message saying that your character is already on the server, and you cannot join. This can be fixed by the host of the server kicking your character from the server. You will then be allowed to rejoin.
 * If you are moving with your character with the Ivy Whip under a 1 block thick surface, and you meet a 1 block thick hole, you may be stuck inside it and be able to jump out.
 * If you grapple in the center of yourself, the game will freeze and crash.
 * Sometimes standing near a chest(Only occurred on Gold Chest) or be in the buy menu near an NPC(With autopause on) will allow you to craft whatever you have items to craft.
 * Sometimes in multiplayer, if a guest to a server places armor on a mannequin, it will not be removed from their inventory, and will be duplicated on the mannequin. This allows for the infinite duplication of any armor already possessed. (Found in 1.1.1)
 * You are able to cast Orb of Light without using mana if your max mana is below 40.
 * On a server, the server host can go onto the single player save of that world, take an item from a chest/safe/piggy bank, and it will still be there on the multiplayer version. This can be used to duplicate infinite items by saving the multiplayer world, and doing it over and over again. (1.1.2 Needs confirmation)
 * There is a limit to how many chests may exist in a world.
 * When entering a world, you can sometimes die from fall damage even though you didn't fall regardless of fall damage cancelling items (even with Lucky Horseshoe in effect.)
 * You can use a grappling hook to go through a 2-block tall space, even though the character is 3 blocks tall. To exploit this glitch, grapple on any block through the space.
 * When you place a music box on a table or workbench, it will duplicate itself and create many copies. (you can sell these for easy platinum coins).
 * On rare occasions when you have closed a door, instead it will be destroyed and until you restart your world it will remain unable to pickup.
 * If you drag the sun while in the title menu and when entering single-player the sun will slowly move where it`s supposed to be. If you do this in multiplayer the sun isn't able to be controlled while connecting. (Confirmed)
 * If you have a grapple on single-player and click anywhere when you minimize Terraria it will make the grapple noise (only if equipped) even though the game is paused because if you minimize single player it pauses. It doesn't move your character when you maximize the screen again.
 * If you receive too many buffs, the game will say "buff overflow" and your character can get deleted. There is no way to get it back except if you have a copy of that character. (Needs confirmation)
 * Sometimes, dropping magical weapons (weapons that use mana) can heal you 20 HP if you don't have full health. (Confirmed)
 * When a player has multiple keys (that unlock Locked Chests) and is planning to open one locked chest, instead of consuming one key, all keys may be consumed. (Needs confirmation)
 * Placing a closed door at your spawn point then respawning will cause the door to break and add two doors to your inventory. This does not work if you chose your bed as your spawn point because doors cannot be placed in beds.
 * Sometimes an endless night without a moon may occur. This can be fixed by exiting the world, then coming back again, to wait for the daytime music to appear after that, though there is a reported case where someone could not fix it by doing so.
 * Sometimes, in hardmode, a message appears stating that the world has been blessed with a 1.1 ore even though no demon altar has been destroyed.
 * Sometimes, without reason, your worlds name can disappear and can't be selected; But oddly makes a gap in your worlds list.
 * Sometimes, your game will crash repeatedly when you try to connect to any multiplayer server (Needs confirmation)
 * Placing a Gold Chest on disappearing stone and activating will break it as usual. But if an Item is placed in it, activating it will break it, yet it will still be there. This can be used to get 100 platinum.
 * If you hook onto a door using grappling hook, and then open the door, it will fling you about 50 meters.
 * When doing the collecting the sand and turning it to bottles  to sell trick you may loose all the money made by that trick but the world will still see the sand blocks and glass as missing.
 * when you use your ice rod to place ice and put a chest on top with an item in it and exit and enter the world you get a floating chest and if you place ice around it the chest will duplicate as long as there are no blocks beneath it (works on multiplayer)
 * On some computers, adjusting the music is impossible. Clicking the - on the music won't do anything, Clicking the + will increase the sound. also, clicking - or + on the sound will both decrase the sound.
 * On some computers that use small monitors, you can't click the EXIT button due to the size of the window. The only way to get around is to turn Terraria fullscreen.
 * If you're game is laggy and you fall some distance and land, there will be no shadows for 1 second granting you the ability to see what's in the shadows and underneath you.
 * If you're game is laggy and you fall some distance and land, there will be no shadows for 1 second granting you the ability to see what's in the shadows and underneath you.

NPCs

 * NPCs continue to occupy a general area even if it is no longer 'suitable' for NPCs. If they die however, they will not come back until the area is suitable again.
 * NPCs will not move into a new house even though it is 'suitable', nor will they re-spawn.
 * NPCs sometimes keep their housing sign up while it is not suitable. But, when you leave the world, the sign won't be there.
 * When purchasing items from an NPC brings you down a coin tier (1 gold coin to 99 silver, etc.) there is a chance the game will register the higher coin as still being there, though the sprite will not show and it can not be spent. This can be fixed by mousing over each coin space in your inventory until you find the invisible coin (the item name and amount will show) and left clicking it. Until it is fixed, the game will attempt to stack all additional money with the nonexistent coin, resulting in lack of funds.
 * NPCs sometimes have pathing issues when attempting to reach their rooms. (Particularly blocks over 3 squares high they can't jump past.) If you reload the world though, they should spawn in their assigned housing.
 * NPCs have pathing issues regarding Wood Platforms.
 * When you spawn for the first time, the Guide can spawn twice for an unknown reason. (Needs Confirmation)
 * Sometimes an NPC will spawn underground and won't be able to climb up.
 * If you have autopause on and are close to an NPC, you will be able to talk to them as if the game was still playing while everything around you will remain still. This can be useful if you are fighting a boss and have low health and the Nurse is near. This only works in single player.
 * Closing a dialogue with the nurse while having the mechanical eye, worm or skull equipped causes "The Twins", "The Destroyer" or "Skeletron Prime" (respectively) to appear without consuming the item (needs confirmation for suspicious looking eye and worm food)
 * Sometimes your Dryad will tell you that your world is 0% corrupt and will not tell you how much hallow there is, this is probably caused by the 1.1.1 update, amid this time many people started experiencing this bug. New items that appeared after the Wall of Flesh were not purchasable, such as the hallow seeds.
 * When you mouse over Santa's banner in housing mode, it says Santa Claus the Santa Claus, instead of using the NPC's name. This isn't much a glitch, more of a fault in the mechanics of the game, since Santa Claus (when mousing over the NPC) only says Santa Claus, much like a Guide might say "Logan" or "Jake" instead of "Guide". So when you mouse over Santa Claus on Housing, it would say Santa Claus the Santa Claus like "Logan" or "Jake" the guide.
 * If you follow an NPC as they go to open closed doors, you are able to walk through. If you follow them just as they are about to close it, the door will disappear.
 * Some NPCs (namely the Clothier, Old Man, the Goblin Tinkerer and the Mechanic) will walk over cliffs they can't climb back up instead of turning around.
 * If you have autopause on when you talk to the Mechanic, Goblin Tinker, or Wizard while they are bound underground, they will stay bound, even though they say they are unbound.
 * Sometimes this may happen without being in the inventory at the same time
 * If you talk to your arms dealer in a world where Skeletron has been defeated and the Wall of Flesh hasn't while your guide is dead, the arms dealer will say the name of the next guide.

Monsters

 * A one block high space allows Slimes to spawn, but also allows them to jump through the floor as most slimes are two blocks high.
 * Demon Eyes can sometimes travel through a 1 block thick layer.
 * If you stand near one of the edges of a map (left, right, top, or bottom), you can see monsters spawn on screen. This is because the monster spawning algorithm considers "offscreen" to be a certain distance from the player, rather than what the camera can actually see.
 * The Slime enemy, if trapped inside a 1 unit space, can travel through walls whenever it tries to jump, which allows it to follow you anywhere around the world unless it "despawns". They can also sometimes jump through 1 unit holes, but this seems to not work when the blocks are made of certain materials, like stone.
 * Rarely, Skeletron will be summoned, kill all players near it then despawn.
 * Some monsters drop more than one Silver Coin, but sometimes when collected it only counts as 1 Silver Coin.
 * The Dungeon Guardian can spawn where you respawn after it kills you.
 * The Destroyer might disappear after about 90% of its health is gone.
 * When you have locked in a Demon in the 'Hell' world, with dirt 4x4 blocks, it is possible for it to go through the layer of blocks that is under it, unconfirmed if it works with any kind of blocks or other monsters.
 * A very rare glitch occurs that says you defeated a boss if you didn't even summon it. Using the magic mirror during the boss hitting you might be the reason if you did that.
 * Sometimes when you break a shadow orb, it doesn't say "A horrible chill goes down your spine..." Instead it will summon the Eater of Worlds without the message "Eater of Worlds has awoken!"
 * Sometimes when a Demon Eye is trapped between 1 layer of blocks above it and a thick layer of blocks below it (that leads to the underground), it may sink down to the thick layer and fade away. (Dirt confirmed)
 * Very rarely a harpy or wyvern may attack you at ground level. This happens when the altitude of the ground is high enough (on top of high hills or mountains) for harpies to appear, and so is more likely to happen in small worlds.
 * When you hook onto a door using any grappling hook, and then open the door, it will fling you about 50 meters very quickly.
 * Chaos Elementals can appear in the Underground Hallow even if hardmode is not active, causing much hassle to pre-hardmode characters.
 * Sometimes the Wall of Flesh will drag you up to the surface and push you past the world boundaries if you survive(band of regeneration required) and crash game.

Map Generation

 * Jungle Shrines can be generated in lava pools with no chest inside them.
 * Jungle Shrines can be generated in the sky (~15 blocks above the ground)
 * In some map instances, it may be impossible to find certain unique items. (Intentional)
 * Chasms can also spawn where dungeons should be, and some times block the way. In this case, you'll need a Nightmare Pickaxe (or above) or purification powder to dig through it, opening the way to the Dungeon.
 * Corruption can be generated within 100 blocks of the main spawn upon initial map creation, without sunflowers blocking them. These Corruptions can spread and cover the spawn.
 * Digging straight down from the spawn point generally leads you to a glowing mushroom biome. However, not always directly into the biome, but always within a screen of the biome.
 * The Underground Jungle sometimes will fuse with the Underground Corruption, causing several/all Shadow Orbs to despawn before the map is even generated fully.
 * Dungeons can sometimes be created in a lake upon initial map creation, submerging the Dungeon entrance. Anything beyond the door of the Dungeon will not be submerged, however.
 * When you create a new world, sometimes the spawn would be in a block. So every time you respawn with blocks in the spawnpoint, the blocks break.

Weapons

 * The effect of Molten Armor applies sporadically to damage from the Ball o' Hurt and Harpoon (not yet confirmed with other flails)
 * If the player's inventory is full (not including arrows) and each of the ammo slots has at least one item in it, there is a bug where the arrows can only be picked up by temporarily displacing one of your items. The type of arrow makes no difference as well as what item you move momentarily. (intentional/insurpassable programming paradox, the ammo must hit your inventory before it will go to the ammo slots)
 * The Dao of Pow can fall through blocks if held in one area and fly under the player if there are blocks under and if the player goes up such as flies up or grapples onto another block, the flail will come out of the ground towards the player even if the player has not gone far enough to make the flail come back to the player forcibly.
 * If a player is on the bottom of the world and controls a projectile made by the rainbow rod then guides it upward to a certain location, the rainbow rod projectile will become invisible but will still be there and if the player moves it out of the certain location downwards the projectile will become visible again.
 * When using a Grappling Hook, if the mouse is aimed at a Wooden Platform above the player and the E key is pressed, then the icon for the Grappling hook in the Hotkeys will disappear when the player grapples to the platform. One must open and close the inventory screen once to fix this.
 * When the player is next to a 1 block thick wall, or a door, and throws a boomerang at it, if the player throws the boomerang in the right direction it will go through the wall or door.

Walls

 * Sometimes the background("Wall") when underground (rocky and mud-rocky) will start to follow you and glitch, jerking about in random motions, there is a known fix to this bug. Turning parallax down to 0 makes it stop. (This is because the 'rocky' walls are actually part of the skybox, and aren't actually back walls. Parallax effects skybox. It's not a glitch.)
 * If a giant worm attacks you while you are next to 1 layer of sand, you may be able to go through it.
 * By running up against a wall of sand, and mining a spot below you, you can run through the space while the sand is still falling. Recommended to use a cobalt/obsidian shield for this to eliminate knockback.

Water
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 * It is possible for a small puddle of water to turn into a never-ending waterfall when the bottom is dug out.
 * An infinite pool of water can be made with a "J" dug into the ground by placing water in the center, taking it out of the shallower side, and repeating.
 * Pumps toggled fast enough will duplicate whatever liquid you have them moving.
 * As of 1.1, water stuck in blocks will disappear if the server is empty or if the game is shut down.
 * As of 1.1, if a player flies into a block with water stuck in it, the player's breath meter would pop and the player could die if they stood still flying on the block while their health goes down after their breath is gone.
 * If a player tries to grapple on a block with water stuck inside it, preferably glass, the hook will detach from the block before the player can get to it. This can also happen on side blocks and propel the player towards the wall(blocks).
 * When you dig any block under water the water will duplicate causing it to be able to flood hell/underworld because the new water does not apply the water fading in the underworld.

Crash

 * The game crashes upon exit from the title screen on some games.
 * If the game crashes unexpectedly, is then restarted and the same world reloaded, all blocks are removed and the player falls directly to the bottom of the map causing them to die. All world data appears gone and cannot be retrieved although map files still exist. (In this case, you can either use Cloud in a Bottle or Rocket Boots to survive the fall at the bottom when the screen no longer centers on your character. Hellbats will spawn out of the bottom of the screen and pools of lava can be found in Hellstone, along with Hellforges. Further exploration has shown that not all blocks in the rest of the world have disappeared, though most have. There will be large amounts of dirt and stone with minerals spread throughout it, but suddenly cuts off at the point where the rest of the world seems to have disappeared.)
 * Putting a laptop to sleep by closing it while in-game can sometimes cause it to crash when you save and quit.
 * Sometimes, when attempting to save and/or exit the game, Windows will notify you that Terraria has encountered an error and needs to close, and thus you will lost any unsaved changes. The cause is suspected to involve the player character, as you can fix the bug by logging in with a different character, saving, and then switching back to the character you were previously using. People who often use multiple characters likely won't encounter this bug.
 * The above bug may also be caused by duplicate world files for the same world slot, and cannot be fixed, only affecting one world. in which case you should go to your computer's start menu and search the file ( formatted as world1 or world2 etc.) and delete the .sav file of the affected worlds, this may delete the world if you select the wrong duplicate (recommended to back up computer before this) but will un-glitch all further instances of this bug.
 * If on server, selecting an item sometimes make the game crash.
 * Sometimes when right-clicking items in a chest or in the inventory, the game crashes. This is often caused by audio devices being disbled, or out of date BIOS or sound drivers.
 * Sometimes editing signs will cause the game to crash.
 * Sometimes placing armor in an armor slot will cause the game to crash if the player is using a non-English language. This is due to missing language files.

Gameplay Multiplayer Cheats

 * Sometimes, holes will inexplicably appear that lead to the bottom of the world. Since this does not happen in singleplayer, it is assumed to be a server-side bug. There is a way to avoid it by placing your base near the left edge of the map from the start, as the "hole" always happen to be on the same spots every time (Picture)
 * If you minimize the server window, the time goes faster (when clicking the server window button in the task bar, might only happen on Windows 7/Vista.). It looks like the sun and moon "teleports" forward. And the monsters are super fast. Maximizing the server window fixes this.
 * Game may crash if you save your spawn point in a bed and reconnect - the server must be reopened.
 * If the players fail to kill Skeletron, the Old Man may not respawn. The players will still get attacked by skulls in the dungeon itself. This bug seems to occur if a spawn location is set within sight of the Skeletron.
 * If players set a spawn point that is at the "end of the world" (past the beach and over the water) and disconnect from the server, they will be unable to reconnect. The reason for this is unknown, and the problem is fixable if the affected players connect to the world in single player and reset their spawn point.
 * Setting a spawn point at a high elevation (i.e. on a floating island) may cause a player to be unable to reconnect.
 * If you start to play on a server for a while you might get kicked and it will say "explosions are disabled on this server" and this will happen for about 10-15 minutes. It is thought to happen when players destroy many blocks within a small time frame on a laggy server and the server recognizes it as an explosion.
 * Eater of Worlds may spawn away from where the third shadow orb was broken, near another player in Multiplayer.
 * Gold Chests may not appear gold to all players. Some Gold Chests may also appear to be part gold to some players. This is fixed on reconnect.
 * Planted flowers may not appear the same to all players (i.e. daybloom may look like blinkroot and vice versa).
 * Shadow Orbs may not appear to be whole (i.e. a quarter shadow orb), but still act like a whole shadow orb (i.e. the quarter shadow orb summoning the Eater of Worlds)
 * Doors will randomly disappear in larger houses.
 * Very rarely the message will appear saying you died if you really didn't, allowing the game to believe that you are "dead" and haven't respawned yet. This allows you to run around without any enemies spawning near you (be careful though, they will spawn near other players). (confirmed, happens on slightly laggy servers while surviving "On Fire!" Debuff with extremely low HP)
 * Continuously firing the Megashark will get you kicked by the anti-cheat.
 * Players may fall through a one-block hole.(Unverified in solo)
 * Sometimes summoning a boss (tested on Eye of Cthulu ) will use up the summoning item but the boss won't spawn. (only tested on multiplayer)
 * You can't stack 100 Gold Coins to make a Platinum Coin. If you try, you won't get any Platinum Coin and your Gold Coins will be gone.
 * If all characters are stacking their money into one source (i.e. a chest or a piggy bank) using the quick stack option, a player's money may occasionally fail to transfer, causing it to disappear.
 * When two players spam opening and closing a door, the door may break and not drop the door item. This may also happen with items such as a lever.
 * There is a bug that occasionally a player (That is not the host) can lose ALL items with no explainable reason. There is no known fix.

Visual

 * Alt-tabbing in and out rapidly can cause unusual colors. Alt-tabbing again fixes.
 * When playing a world for the first time there is a chance no HUD/GUI is displayed. (Can be fixed by pressing F11)
 * Moving to fullscreen causes all things to speed up i.e. the sun and moon move at an increased pace. The cursor also speeds up, this also affects single player. (multiplayer not known) It is widely suspected that this is because your monitor's refresh rate overwrites the game's when running it in fullscreen.
 * When running the game in windowed mode, clicking on another window that doesn't cover the Terraria window will cause any light from Mining Helmets and armor sets with lighting effects to vanish (does not occur in multiplayer). Clicking back into the window allows it to light correctly. This does not affect the game, as it pauses when another window is clicked.
 * The lighting effect of a meteor crash site may remain even when all meteor blocks have been mined.
 * When Hellstone and lava stop glowing, (in The Underworld) the Rocket Boots fire particles, the Flamelashes trail, and the Molten Armors glow particles are no longer visible.
 * For unknown reasons, attack font can sometimes be distorted and glitch into unrecognizable numbers. Example. This bug does not affect critical attack numbers, and can be fixed by simply leaving and re-entering the affected world.
 * When using Dynamite on Ebonstone it will explode and leave a gap for a moment, but then it looks like there was no explosion. The blocks that reappear will be solid and the ones that exploded will be trapped inside the blocks that reappeared. (other blocks unconfirmed)
 * Sometimes, when moving to fullscreen and then switching back to normal, only half the game is visible.

Audio
These are the bugs related to the Terraria audio.
 * Both the day theme and night theme can play at the same time if the change happens on the instant of the current song being re-looped. This will last until the theme playing before the change of day/night starts a new loop.
 * For some reason, the Hallow theme does not seem to play if the biome was entered at night.

Item Cloning
These bugs cause you to be able to clone items. Keep in mind that cloning means duplicating. If you want ITEM X, but do not have it, obviously you cannot clone it.

Running two instances of Terraria
To clone items in Terraria single player; open 2 copies of Terraria, and in both copies, sign in with the same character. In COPY A, open WORLD A, and in COPY B, open WORLD B. In WORLD A, put ITEM X in a chest. Save and exit to the title screen and exit the game client. Open COPY B and save and exit the world. Do not close COPY B. Enter WORLD A and go into the chest you put ITEM X in. ITEM X will be in the chest and also in your inventory. {C}This method works because when you save and exit WORLD A, ITEM X is saved inside the chest. However, because you have 2 inventories opened, ITEM X will stay in your inventory in WORLD B. So, when you go into WORLD A again, you will still have ITEM X in your inventory. (Sorry about all the As and Bs)

(It looks like steam updated and so it will no longer let you run two instances of any game. I honestly don't know this for sure, but it is the case with my computer.)

Tips to copying character files and world files
If you decide to clone items by copy/paste world or character files, be sure to know which file is which: player1.plr appears below player1 - Copy.plr, which also appears below any subsequent copies (of which copy 2 comes at the top, and then 3, etc.) of the player file. To be sure which copy you are using (or the original), please know that the order of the characters found in the Terraria character selection screen mirrors the order found the the "Players" folder. The same is for world files.

Closing a server or disconnecting abruptly
Item cloning can also be performed by placing an item in a container on any server, saving the server, then starting it again. Once the player revisits the container, if they take the item, disconnect, then close the server improperly (such as alt + F4 on the server tab) without letting it save, the item can be found yet again in the container. For example: A Video Showing this method can be found here
 * 1) Player A leaves ITEM X in a chest.
 * 2) Player A disconnects.
 * 3) Server is disconnected/saved.
 * 4) Server is reconnected.
 * 5) Player A connects and takes item.
 * 6) Player A disconnects.
 * 7) Server is closed abruptly without saving the map.
 * 8) Server is reconnected.
 * 9) Player A joins.
 * 10) Player A takes ITEM X and now has a duplicate.

Another example:
 * 1) Player A drops an item in a server.
 * 2) Player A disconnects abruptly.
 * 3) Player A rejoins server.
 * 4) Item is still in Player A's inventory as well as in the server.

If you have played for a long time in your current session, make sure you disconnect and then reconnect to the server before you start duplicating items, or you will lose items you obtained recently. (Because the server did not have a chance to save them.)

Mass produce items from chests, involving two players
You can create and mass produce items in multiplayer from chests, to do this you require some teamwork with another player, player A puts 1 gold ore in a chest slot, player B checks the chest, player A removes the gold ore, player B can now right click the spot were the gold originally was and obtain a gold ore, he can then proceed to right click empty chest slots to increase the number of ores he has, however, these ores are nameless and can-not be used in crafting, but they can be placed on the ground then mined, now with a name and now craftable, since this can be done with any ore, all endgame items can easily be obtained after the players obtain at least one Adamantite Ore. It should also be noted that players are able to sell the nameless items for the same worth of the item being duplicated, letting players duplicate endless diamonds for consistent coins, dropping any nameless items results in the item being randomly made into something else with exactly the same number in the stack but is still nameless.

Duplicating entire worlds
The second easiest way to clone items is to simply clone the item world file. This can be done by opening the Start Menu, going to Documents, going to My Games, then clicking the Terraria folder, then the World folder, then copying the world file, pasting it in the World folder you are already looking at, and then renaming it as another world. This can only be done if you have less than 5 worlds. For example if you only have 1 world the World folder will say, "world1.wld" and "world1.wld.bak". You can copy world1.wld and paste it again and it will be named "world1 - Copy.wld". Rename this as "world2.wld" and then exit the folder and start Terraria. The game will assume this is just your second world file but it will really be an exact copy of your first world.

Duplicating characters
A method is to go into the player file and copy the character. For example you have player3.plr and player1.plr, copy player3.plr into the players folder, then rename the copy to player2.plr. This will result in a clone of the player which has the same items as the player that was cloned. This is a very efficient way of farming anything.

Doors in lava
There is also a way to duplicate doors by placing a thin layer of lava on the ground that does not hurt you and placing a door in a doorway. Once you have placed the door, right click it continuously, do this and you will have stacks of doors, if you require them. This means that you will get infinite doors for any use.

Infinite Chests
By placing chests (must have something in them) on top of active blocks an triggering the blocks, chests will spawn at a ridiculous rate. This can very quickly fill your inventory (less than 12 seconds). If gold or shadow chests are used, this can generate huge amounts of money quickly, as a full stack of 99 gold/shadow chests sell for.

Infinite reforged items
There is a way to clone any item that can be reforged. By talking to the Goblin Tinkerer and selecting "reforge", place the item you would like to clone in the box, now you can choose to reforge or just click "Save and Exit" when you Save and Exit simply reload your last character and world and the item that you placed in the box will drop in front of your character. (Proof needed that this method still works.)

Infinite Music Boxes
If you place a recorded Music Box on a Table or Workbench, it will multiply and each can be sold for. This bug has been fixed in Terraria 1.1.1

Single Player
These bugs only happen in Single Player mode.
 * If player and an NPC opens the door at the same time, the door disappears.
 * Parts of your home can disappear for no reason. (this may be caused by you creating your house at the spawn, then spawning, which causes the game to delete any blocks in your way)
 * In single player with frame skip off and in windowed mode, clicking the Terraria task bar icon to minimize the window, will cause the game to drastically speed up.
 * Chest contents sometimes disappear.
 * Opening a door while wiring over the door opens it simultaneously, the door will disappear. (Needs confirmation)
 * As of 1.1, players wearing shadow armor with the green phasesaber equiped can glitch through walls by grappling into the wall and swinging the phasesaber at the moment of impact. This only works with the green phasesaber and will often times result in getting stuck in the wall and not being able to get out. ** Yet to be tested or confirmed.

Fixed Bugs
These notable bugs have been fixed and no longer exist in the current version of Terraria.

General:

 * After knocking down a large tree, pieces of wood get stuck underground and stay there until you dig them out.
 * Place a door under water and constantly open and close it. The water will slowly disappear up to the base of the door. This is probably caused by the water in the 3 blocks that the door occupies being destroyed when the door is closed. (Water can now occupy the same space as a closed door, showing the door behind the water.)
 * Dirt no longer mixes with sand when controlled with the Dirt Rod, Instead, the dirt breaks, and can be picked up.
 * In mediumcore, when you die, if an item is in the trash bin spot, it will stay with you when you die.
 * If you kill yourself and, right before you die, take your money out of your inventory by left clicking it, half of your money will still drop where you died, but you will still have your original stack. Basically multiplying your money by 1.5. making it possible to get unlimited money.
 * Oceans may spawn where Dungeons should be, causing the entrance to the dungeon to only sometimes be visible/accessible.

NPCs:

 * NPCs may fail to spawn, even though there are valid houses in the world and conditions are met.

Monsters:

 * Creating an artificial jungle: even if the depth meter says you're below sea level, hornets or man eaters will fail to spawn.
 * In the Underworld, Piranhas will spawn in lava causing them to die the instant they spawn.

Weapons

 * In mediumcore if a weapon with modifiers is dropped upon death the weapon will lose it's modifiers. (This has been fixed in the 1.1.1 update)

Multiplayer:

 * A problem in the Client-Server synchronization causing monsters to suddenly teleport to another location when they are dealt damage by the player. (If this still happens, it's because of a bad host.)
 * The game may crash when you break 4 Shadow Orbs in a row.stake