|Catches fire from lava||
An observer is a block that emits a redstone signal when the block or fluid it faces experiences a change.
An observer requires a pickaxe to be mined. When mined without a pickaxe, it drops nothing.
- Times are for unenchanted tools as wielded by players with no status effects, measured in seconds. For more information, see Breaking § Speed.
Redstone Dust +
An observer is placed similarly to a piston. It observes the block that it is placed against. The texture of the detecting side is that of an observing face. As observers can detect the state of other observers, placing two adjacent observers, each watching the other, can make a fast and compact redstone clock. They send out a pulse.
In Java Edition, an observer detects changes in its target's block states, or the breaking or placing of a block (i.e. changes in its block state, but not its block entity data). This means that changes like the age of crops can be detected, because they are part of the block states.
In Bedrock Edition, an observer acts as a block update detector, and detects anything that causes a block update in that edition.
Causes and propagation of block updates are different between Java Edition and Bedrock Edition. As a result, each can detect some kinds of changes that the other cannot. See the table below for a comparison.
When it detects something, the observer emits a redstone pulse of strong power at level 15 for 2 game ticks (1 redstone tick). The pulse can power redstone dust, a redstone comparator, a redstone repeater, or any mechanism component located at its opposite end.
In Java Edition, the pulse is emitted with a delay of 1 redstone tick. In Bedrock Edition, it is supposed to be delayed by 1 tick as well, but is actually delayed 2 redstone ticks due to , a bug causing redstone delays to be incorrect when components are activated by world changes (which, in the case of the observer in Bedrock Edition, is the only way it can be activated), as opposed to pure redstone components ticking. Its timing can also be incorrect due to .
It also counts as a block update when the observer itself is moved by a piston. When this happens, an observer emits a pulse after being pushed or pulled, but not beforehand.
Though they block light, observers behave as transparent blocks do in one sense: they cannot be powered by an external power source, nor power themselves with their own output.
Because observers in Java Edition detect changes in the block state, and not block updates, they can detect a wider range of phenomena than a block update detector (BUD) circuit in Java Edition can detect (as some block state changes don't cause block updates). Observers in Bedrock Edition do detect block updates but not block state changes, and so they detect the exact same things that any other BUD would detect in that edition.
|Kind of block update||Bedrock Edition||Java Edition|
|Changes to the block states of fire that signifies flammable surfaces surrounding fire||No||Yes|
|Opening and closing chests and ender chests||No||No|
|Opening and closing shulker boxes||No||Yes|
|Opening and closing barrels||Yes||Yes|
|Changes to inventory of any blocks that comparators measure as containers||No||No|
|Activating / deactivating a beacon||Yes||No|
|Success of a command block||No||No|
|Activation / deactivation of a hopper (Turning the hopper on/off)||Yes||Yes|
|Dry farmland changing among its six dry-looking hydration stages||No||Yes|
|Farmland going between dry and humid||Yes||Yes|
|Activation / deactivation of a dropper or dispenser||Yes||Yes|
|Activation / deactivation of redstone ore||Yes||Yes|
|Spread of grass to dirt, or decay of grass into dirt||Yes||Yes|
|Aging of saplings, sugar cane or fire||Yes||Yes|
|Moving potions to / from a brewing stand||Yes||Yes|
|Activation / deactivation of a dragon head||Yes||No|
|Placing / removing an item frame, adding / rotating / removing an item in an item frame||Yes||No|
|Teleporting something by the end gateway||Yes||No|
|Adding / removing contents from a flower pot||Yes||Yes|
|Locking / unlocking and changing delay of a redstone repeater||Yes||Yes|
|Changes in the shape of walls, fences, iron bars, glass panes, stairs, tripwire, redstone, vines, melon stem or pumpkin stem||Yes||Yes|
|A grass, mycelium, or podzol block becoming snowy or not snowy||Yes||Yes|
|Playing a note block||No||Yes|
|Forced growth of sugar cane by bone meal||Yes||Yes|
|Door is opened or closed||Yes||Yes|
|Tripwire is intersected, even if not attached to a hook||Yes||Yes|
|All other block / block state changes||Yes||Yes|
|Water level changes||Yes||Yes|
Observer can be placed under note blocks to produce "bass drum" sound.
|Sound||Subtitle||Source||Description||Namespaced ID||Translation key||Volume||Pitch||Attenuation|
|Block broken||Blocks||Breaking the block||1.0||0.8||16|
|None[sound 1]||Blocks||Falling on the block with fall damage||None[sound 1]||0.5||0.75||16|
|Block breaking||Blocks||Mining the block||0.25||0.5||16|
|Block placed||Blocks||Placing the block||1.0||0.8||16|
|Footsteps||Blocks||Walking on the block||0.15||1.0||16|
|Blocks||Breaking the block||1.0||0.8|
|Blocks||Falling on the block with fall damage||0.4||1.0|
|Blocks||Mining the block||0.37||0.5|
|?||Blocks||Jumping from the block||0.12||1.0|
|?||Blocks||Falling on the block without fall damage||0.22||1.0|
|Blocks||Walking on the block||0.3||1.0|
|Blocks||Placing the block||1.0||0.8|
|Name||Namespaced ID||Translation key|
|Name||Namespaced ID||Numeric ID||Translation key|
In Bedrock Edition, observers use the following data values:
Three bits storing a value from 0 to 5:
|0x8||If set, the observer is powered.|
|Name||Default value||Allowed values||Description|
|facing||The direction the observer is observing. The same direction the player faces when placing the block.|
|powered||True while the observer is observing a change and emitting a pulse.|
|Name||Default value||Allowed values||Description|
|facing_direction||The direction the observer is observing. The same direction the player faces when placing the block.|
|powered_bit||True while the observer is observing a change and emitting a pulse.|
|November 24, 2012||When announcing the upcoming 1.5 Redstone Update, Jeb mentions that changes to redstone logic may break existing BUD functionality, and therefore that block update detection may need to be implemented into the game in a more permanent, intentional form, rather than as a behavioral quirk.|
|Note: the "arrow" texture on the top/bottom of observers is pointing the wrong direction (toward the input, rather than the output).|
|Observers act as a block update detector.|
|Observers emit pulses that lasted 1 game tick (0.5 redstone ticks) and have a signal strength of 1.|
|Observers can power blocks (like a redstone repeater).|
|Observers have no delay between detecting a block update and emitting a pulse, meaning that observers are essentially instant.|
|Observers are placed with the observing, or input, side facing the player.|
|16w41a||Observers now emit 4 game tick (2 redstone ticks) pulses.|
|The signal strength of observers has now been changed to 15.|
|Observers *appear* to no longer strongly power blocks, and now emit only activation power, like a block of redstone (and this may be the intended behavior for this snapshot). However, in reality, they still strongly power blocks, but the blocks adjacent to those blocks aren't given block updates, causing buggy behavior.|
|Observers are now placed with the output facing the player.|
|A bug where observers would redirect redstone dust from all 4 directions has now been fixed. (They are supposed to redirect dust only from their output side.)|
|16w42a||The developers have attempted to make observers no longer detect block updates happening to air blocks, in order to make observer behavior more predictable. In the process, they have broken redstone mechanics a bit, so that the block update bug from the previous snapshot now affects redstone repeaters and redstone comparators, too.|
|16w43a||The texture of observers has now been changed. The rotation of the "arrow" texture has now been fixed so it points in the correct direction.|
|General redstone mechanics for observers now work as they did before 16w42a, with the exception of the change named below.|
|Observers now output strong power like in 16w39a, except that they, as well as redstone repeaters and redstone comparators, no longer provide block updates to transparent blocks or air.|
|16w44a||The observer block update changes relating to redstone from 16w42a and 16w43a have now been fully reverted.|
|The behavior of observers has now been overhauled/redefined. Observers have now been changed from a block update detector to a block state change detector.|
|Observers have now been changed to detect when the block it was observing changed, its basic block state changed, or the block was placed/destroyed. (Note that it does not detect changes in the extended block state, e.g. changes that are not saved when the world is unloaded, such as the shape of a fence, or whether or not a repeater is locked.) This change has now made observer behavior much more predictable, as unexpected/invisible block updates would no longer trigger observers.|
|Observers have now been changed to emit a 2 game tick (1 redstone tick) pulse when activated.|
|Observers no longer output power instantly.|
|pre1||The front (detecting side) texture of observers has now been changed to be an 'observing face'. The "arrow" texture on the top/bottom of the observer has also been modified.|
|The redstone output side of observers now blinks red when it outputs power.|
|1.13||17w47a||Prior to The Flattening, this block's numeral ID was 218.|
|Due to The Flattening, observers can now detect all block state changes, e.g. the changes in the shape of fences and redstone dust.|
|pre4||Observers no longer produce a pulse when placed by hand.|
|1.14||18w43a||32px The texture of observers has now been changed.|
|1.16||20w10a||Observers can now support ladders and tripwire hooks.|
|20w14a||Observers now correctly detect when the status of the fence changes.|
|Pre-release 3||32px The back texture of activated observers has been changed.|
|Pocket Edition Alpha|
|0.15.0||May 2, 2016||Jeb tweeted that Daniel Wustenhoff is a working on a BUD block.|
|Tommaso Checchi tweeted his "rejected graphics" for the observer block.|
|build 1||Added observer blocks.|
|0.15.3||Observers are now placed like a piston and not a log.|
|1.2.0||beta 188.8.131.52||The texture of observers has now been changed.|
|Observer blocks can now detect many more block changes.|
|The strength of the redstone pulse outputted by observer blocks has now been increased.|
|Observers no longer pulse twice when observing a retracting piston.|
|Opening and closing the command block screen no longer activates an observer block.|
|1.10.0||beta 184.108.40.206||The texture of observers has now been changed.|
|1.16.0||beta 220.127.116.11||Observers no longer emit a pulse when they are first placed.|
|Legacy Console Edition|
|TU54||CU44||1.52||Patch 24||1.0.4||Added observers.|
|1.90||The texture of observers has now been changed.|
|New Nintendo 3DS Edition|
- When moved by a piston, an observer sends a 2-game tick (1 redstone tick) pulse after being moved, which makes it useful for slime block flying machines.
- The current Observer texture was created because Jeb kept confusing the front with the back. He said it was inspired by the "rejected texture" created by Tommaso Checchi.
- Melon or pumpkin stems that become attached to the melon or pumpkin are detected in Java Edition, and Bedrock Edition.
- Includes firework rockets, falling block entities, fishing hooks, entities (ie. fireballs, lama spit, evoker fangs etc.) and all throwable projectiles other than splash/lingering potions and enderpearls.
- "Hype train! @darngeek is working on a device that acts as a proper BUD block in MC:PE (PC eventually), currently called "Observer"" – @jeb_, May 2, 2016
- "Here's my rejected graphics for the Observer, because @darngeek has no artistic sensibility" – @_tomcc, May 2, 2016
- "I kept confusing myself which side was front and back, so here's something inspired by the works of @_tomcc http://i.imgur.com/IK2d8m2.png" – @jeb_