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Observer

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Observer
Observer JE4 BE3.pngObserver (back) JE2.gif
Renewable

Yes

Stackable

Yes (64)

Tool

Blast resistance

3.5

Hardness

3.5

Luminant

Yes

Transparent

Partial

Flammable

No

Catches fire from lava

No

An observer is a block that emits a redstone signal when the block or fluid it faces experiences a change.

Obtaining[edit]

Breaking[edit]

An observer requires a pickaxe to be mined. When mined without a pickaxe, it drops nothing.

Block Observer
Hardness 3.5
Tool
Breaking time[note 1]
Default 17.5
Wooden 2.65
Stone 1.35
Iron 0.9
Diamond 0.7
Netherite 0.6
Golden 0.45
  1. Times are for unenchanted tools in seconds. For more information, see Breaking § Speed.

Crafting[edit]

Ingredients Crafting recipe
Cobblestone +
Redstone Dust +
Nether Quartz

Usage[edit]

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 pulsing redstone signal.

Behavior[edit]

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 MCPE-15793, 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 MCPE-73342.

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.

Limitations[edit]

[needs in-game testing]

Detected in
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, ender chests and shulker boxes No Yes
Changes to inventory of any blocks that comparators measure as containers Yes No
Activating / deactivating a beacon No No
Success of a command block No No
Activation / deactivation of a hopper (Turning the hopper on/off) Yes N/A
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[1] or pumpkin stem[1] 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 N/A
Door is opened or closed Yes Yes
All other block / block state changes Yes Yes


Sounds[edit]

Java Edition:

SoundSubtitleSourceDescriptionNamespaced IDTranslation keyVolumePitchAttenuation distance
Block brokenBlocksBreaking the blockblock.stone.breaksubtitles.block.generic.break1.00.816
None[sound 1]BlocksFalling on the block with fall damageblock.stone.fallNone[sound 1]0.50.7516
Block breakingBlocksMining the blockblock.stone.hitsubtitles.block.generic.hit0.250.516
Block placedBlocksPlacing the blockblock.stone.placesubtitles.block.generic.place1.00.816
FootstepsBlocksWalking on the blockblock.stone.stepsubtitles.block.generic.footsteps0.151.016

Bedrock Edition: [needs in-game testing]

SoundDescriptionNamespaced IDVolumePitch
Breaking the blockdig.stone? 0.8
Falling on the block with fall damagefall.stone? ?
Mining the blockhit.stone? 0.5
?Jumping from the blockjump.stone? ?
?Falling on the block without fall damageland.stone? ?
Walking on the blockstep.stone? ?
Placing the blockuse.stone? 0.8

Data values[edit]

ID[edit]

Java Edition:

NameNamespaced IDTranslation key
Observerobserver block.minecraft.observer

Bedrock Edition:

NameNamespaced IDNumeric ID Translation key
Observerobserver 251tile.observer.name

Block data[edit]

In Bedrock Edition, observers use the following data values:

Bits Values
0x1
0x2
0x4

Three bits storing a value from 0 to 5:

  • 0: Observer facing down
  • 1: Observer facing up
  • 2: Observer facing north
  • 3: Observer facing south
  • 4: Observer facing west
  • 5: Observer facing east
0x8 If set, the observer is powered.


Block states[edit]

Java Edition:

Name Default value Allowed values Description
facingsouthdown
east
north
south
up
west
The direction the observer is observing. The same direction the player faces when placing the block.
poweredfalsefalse
true
True while the observer is observing a change and emitting a pulse.

Bedrock Edition:

Name Default value Allowed values Description
facing_direction00
1
2
3
4
5
The direction the observer is observing. The same direction the player faces when placing the block.
powered_bit00
1
True while the observer is observing a change and emitting a pulse.

History[edit]

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The specific instructions are: Why do we even need to know about Pocket Edition in the Java Edition history?
Java Edition
November 24, 2012When 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.
1.1116w39aObserver JE1.png Added observers.
Note: the "arrow" texture on the top/bottom of observers is pointing the wrong direction (toward the input, rather than the output). This is not noticed by most people, though, since the observer in Pocket Edition has a texture bug where the top and side textures do not rotate properly (except the output/input sides), causing the arrow texture to always point in the same direction.
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.
16w41aObservers now emit 4 game tick (2 redstone ticks) pulses.[2]
The signal strength of observers has now been changed to 15.[3][4]
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.[5]
Observers are now placed with the output facing the player.[6][7]
A bug where observers would redirect redstone dust from all 4 directions has now been fixed.[8] (They are supposed to redirect dust only from their output side.)
16w42aThe developers have attempted to make observers no longer detect block updates happening to air blocks, in order to make observer behavior more predictable.[9] 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.[10]
16w43aObserver JE2.png 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.
16w44aThe 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, AKA 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.[11]
Observers have now been changed to emit a 2 game tick (1 redstone tick) pulse when activated.[12]
Observers no longer output power instantly.[13]
pre1Observer JE3.png 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.
1.1317w47aPrior 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.
pre4Observers no longer produce a pulse when placed by hand.
1.1418w43aObserver JE4 BE3.png Observer (back) JE1 BE1.gif The texture of observers has now been changed.
1.1620w10aObservers can now support ladders and tripwire hooks.[14]
20w14aObservers now correctly detect when the status of the fence changes.
Pre-release 3Observer (back) JE2.gif The back texture of activated observers has been changed.
Pocket Edition Alpha
0.15.0May 2, 2016Jeb tweeted that Daniel Wustenhoff is a working on a BUD block.[15]
ObserverRejectedGraphics.png
Tommaso Checchi tweeted his "rejected graphics" for the observer block.[16]
build 1Observer BE1.png Added observer blocks.
0.15.3Observers are now placed like a piston and not a log.
Bedrock Edition
1.2.0beta 1.2.0.2Observer BE2.png 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.
1.10.0beta 1.10.0.3Observer JE4 BE3.png The texture of observers has now been changed.
1.16.0beta 1.15.0.53Observers no longer emit a pulse when they are first placed.
Legacy Console Edition
TU54CU441.52Patch 241.0.4Observer JE3.png Added observers.
1.90Observer JE4 BE3.png The texture of observers has now been changed.
New Nintendo 3DS Edition
0.1.0Observer BE1.png Added observers.

Issues[edit]

Issues relating to "Observer" are maintained on the bug tracker. Report issues there.

Trivia[edit]

  • 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.[16][17]

Gallery[edit]

See also[edit]

References[edit]