What Does An Observer ACTUALLY See?

A complete list of literally EVERYTHING that an observer can detect. Hopefully at least... Research was crazy...
Chapters:
00:00 Intro
00:28 What does an observer do?
01:51 The Common Denominator
02:20 Building Blocks
03:21 Colored Blocks
03:57 Natural Blocks
10:08 Functional Blocks
12:10 Redstone Blocks
15:31 Broad Categories
16:59 Special Cases
17:51 Outro

[@yowza234]

I genuinely enjoy the imagery of an observer getting so briefly excited it momentarily shits itself energy for a tick and immediately regains stoic composure

[@Mr.Carrot]

At this point, a list of what the observers *can't* detect would be more useful

[@fortrress]

no this is way more fun

[@TrialBySquire]

Minecarts passing by, unfortunately

[@mohitonon-alco4287]

​@@TrialBySquirethey aren't block updates, and you have detector rails for that purposr

[@DeltaDoesGarbaj]

​@@TrialBySquireno f*cking way

[@ConcavePgons]

Bedrock Edition observers detect much less than Java.

[@WhoosferToo]

"when it grows" my fav line of this video

[@not_vinkami]

When it gross

[@duckified.]

what i say when she asks "when can we start?"

[@ryguy-qh2qk]

when does he say that

[@nikkosstorychannel]

​​​@@ryguy-qh2qk 5:45 6:51

[@ToxicBronyRoseAlt]

When he said "when it grows" I felt that too. Who else?

[@caspermadlener4191]

1. Redstone ore doesn't power when you place a block against it, only when you right or left click it. This is noticeable when you shift-click a block against it. 2. You forgot the dragon egg. 3. Pistons heads aren't oberved when trying to retract slime over pull limit. 4. When you clip the end of some plants, it is detected.

[@jazziiRed]

If you're referring to the dragon egg teleporting, then yes I did overlook that. Also, I did not know that about piston heads, thanks!

[@Endless-fire]

@@jazziiRed they are refering to how in Java Edition, certain plants stop growing if shears are used on the tip.

[@xecron9116]

For those wondering what condition the observer checks, it typically reads the *blockstate* in front of it. A blockstate is a variable containing data on the block at that XYZ position which is used to change how certain blocks behave, how they look, and (you guessed it) to detect changes at a point. When the block in front of an observer is removed, placed, or updated through some behavior or player interaction. The data in the blockstate is changed, which is detected by the observer resulting in it sending a signal behind it. Also, the data within the observer's blockstate is changed when it detects something, which is why you can chain observers.

[@Uranium-jj7le]

>Observer checks changes in blockstates Observer when observing a change, changes its blockstate Thank you random mojang dev

[@GeeBeeOhThree]

​@@Uranium-jj7leI think that goes back as far as introducing blockstates, there's no way it COULD give a pulse without it unless it just...didn't have blockstates...which is impossible

[@majorjohnson8001]

@@GeeBeeOhThree is correct here. "Powered" is considered a block state property, and it's this property that a lot of redstone blocks check for...redstone power (along with another property for signal strength, for those blocks that use it). All rails use the same state properties, too (the non-cornering being a restricted subset). Crop ages are similar, though there are like six variants (based on the max age value). Gravity blocks falling is--likewise--due to the block turning into an entity (just like TNT). As far as the observer is concerned, the block ceased to exist, just as if it was destroyed. The campfire cooking items being placed and removed *isn't* a blockstate change, even though it involves a visual update. Because there are many kinds of cookable food (and mods can add them), that information isn't encoded in the blockstate (the list of valid states cannot be altered), but rather in the block entity itself as inventory. Those inventory items are then specially rendered by the entity renderer (which basically delegates back to the item renderer, with some transformations so it appears in the desired location and rotation). Chest opening/closing is handled even more differently, though I forget exactly how it works. Some data is stored in the block entity, but its animation state is separate from that iirc. Comparators and the trapped chest outputting a redstone signal is bespoke logic.

[@mooing_cowmilk]

One major thing observers can't detect is rapid changes, which breaks most age based farms, or fast tick block streams. Other items it can't detect is the creation of the nether portal block (lighting a nether portal), change text color of signs, left clicking a note box (in survival plays it but not detect).

[@widmo206]

Changing the color of a sign is probably because you're not changing the block itself, but rather it's tile entity, which I guess doesn't create a block update

[@broski7792]

My two favourite are string when an entity enters or leaves it's hitbox, and note blocks when you change the instrument underneath. I used the string one to make an automatic water dispenser for the riptide enchantment. When you stand in it, it dispenses water at your feet so you can riptide, and then when you leave, it triggers the dispenser again, getting rid of the water. I've never really used the note block one, but it's a neat mechanic which can help you distinguish between blocks in some scenarios, like a block stream. Edit: |-_-|

[@jazziiRed]

That's a nice little contraption. I like it! |-_-|

[@u12bdragon]

Observers are more like [-.-_-.-] i think

[@olegmoki]

|т_т|

[@F17A]

Heard of pressure plates?

[@duckified.]

@@F17A pressure plates have to be placed on full blocks, string is more versatile

[@Juni_Dingo]

Such a criminally underrated channel, you deserve so much more attention |-_-|

[@jazziiRed]

Thank you! |-_-|

[@martitoto9715]

so true

[@martitoto9715]

@@jazziiRed just take all my subs im not worthy for them like u

[@MyMe-hh9cs]

true

[@Some1NamedPlays]

yes

[@FarTheGoober]

Genuinely couldn’t believe how small this channel was. Video quality is amazing and it’s clear you put a lot of time and effort into this video!! I’ll be glad to be along the ride do you getting famous because this deserves more recognition!

[@jazziiRed]

Thank you! Glad to have you here :)

[@limeflashlight4101]

I agree

[@Kokonutzlz]

9:17 it should also detect when the sponge evaporates :) It's not just a furnace recipe, it happens automatically in the Nether. The string thing is really cool, as you don't need a more visible tripwire hook setup to activate it getting walked on. The hard part is now to hide the observer 🤔

[@jazziiRed]

I thought about adding that, but it happens so instantly that the observer doesn't have a chance to detect it. It's still on cool down from detecting you placing it.

[@Nulono]

@@jazziiRed Could that and the cactus limitation be bypassed by commands?

[@alonsomartins712]

probably

[@c42xe]

@@Nulono I think as long as the cactus is not updated. But it should destroy itself when its updated.

[@ScAr_wlvrne]

@@jazziiRed iirc, sponges dry out slowly in deserts, badlands, and maybe savannas too Edit: missed the Bedrock only disclaimer on the wiki

[@beefox__]

a common denominator for most of these are blocks and block states, anything that changes a block state (stair shape), or the block entirely (dirt turning to grass), there are some exceptions to this rule

[@noxmore]

I thought this was the only rule, what are the exceptions? (also blocks changing entirely count as block state changes internally)

[@hyper_lynx]

​​@@noxmore There aren't any exceptions as far as I know, the Observer activates whenever the block in front of it changes state. (Whenever its updateShape() method is called by a block changing in front of it)

[@noxmore]

@@hyper_lynx yeah that's what i thought as well

[@lordmarum]

Very clear and fun to watch. Great videos!

[@jazziiRed]

Thanks!

[@KidPrarchord95]

Thank you for doing this! I remember thinking the scaffolding one was cool when I figured it out, so I'm glad to see that little trick being spread to a wider audience.

[@mimixte]

I already knew what the observer is used for but I must admit that some of these where new to me (like the scaffolding or the leaves), thank you for this amazing lesson professor |-_-|

[@jazziiRed]

You're very welcome |-_-|

[@kirisummer]

I would categorize updates a bit differently, since lots of interactions could be described as "replacing an observed block", like when blocks are turned into moss or (cobble)stone from lava and water interactions, "changing amount" for turtle eggs, sea pickles or candles, or being more concise with grouping all "growable" blocks (crops, trees, bamboo, etc) into one category, but it's a good video nonetheless C:

[@jazziiRed]

For sure, that's what's going on behind the scenes with a lot of these. But I wanted to present it in a way that's easiest to understand for most people. Plus, the effect is the same whether you think of a sapling being replaced by a log or it growing. Totally understand where you're coming from tho.

[@hyper_lynx]

Behind the scenes, I'm almost certain all of these are the BlockState changing. Each of these blocks have multiple possible states they can occupy (for example, a slab block can be lower half, top half, and a double slab). Interestingly, changing a block to an entirely different block and just changing its state are internally very similar, and in both cases the function that Observers listen for is called. If you want to play around with this, you can try using the Debug Stick to manually alter the state of any block and see the combinations for yourself.

[@steelspyder474]

You're gonna be huge someday! Awesome Job dude... I love everything about this video

[@jazziiRed]

Thanks!

[@hw2007]

6:05 "Just play around with it, it gets excited easily" I caught that ;)

[@GingerMoony]

Basically a redstone ore block is just an observer extension right? It observes more than an observer

[@hw2007]

@@GingerMoony Never thought of it that way, but I guess so yes!

[@duckified.]

@@GingerMoony nope, only entities

[@SETHthegodofchaos]

Shower Thought: Does the Observer actually observe or is it subscribing and being notified? 🤔

[@goodiesohhi]

I would presume it would make more sense for every block to be a subject and notify any observers next to it. So observer pattern for sure. That's probably why it was named as such honestly.

[@TheHighWizardCat]

ok but the vertical walls, leaves and scaffolding ones are EXTREMELY interesting, i could defo see some potential for those

[@Endless-fire]

leafstone and scaffolding is useful for compact vertical/twisted lines and walls and powered rails are useful for instant transmission.

[@SharkfightersSH]

90.3% done on your way to 10k, well deserved.

[@EquaTechnologies]

The observers can activate also when leaves are "charged" by wood. Nice video too!

[@ImAuriss]

Observers can observe "block state changes" so any block that you can directly interact with or natural game state changes.

[@mystictnediser3854]

The leaves trick with the messured distance to the next log is extremely useful

[@HattmannenNilsson]

Very informative video. The title puts me in mind of a passage from Philip k. Dick's "A Scanner Darkly". "What does a scanner see? he asked himself. I mean, really see? Into the head? Down into the heart? Does a passive infrared scanner like they used to use or a cube-type holo-scanner like they use these days, the latest thing, see into me - into us - clearly or darkly? I hope it does, he thought, see clearly, because I can't any longer these days see into myself."

[@wChris_]

Its actually pretty simple. |-_-| detect block state changes, i.e. if you open F3 the things at the lower right when looking at blocks. Block state changes also include blocks changing outright, like converting grass to dirt, because they are 2 distinct blocks.

[@jazziiRed]

Yep, that's the gist

[@JP913.]

you are about to hit 10k , im part of the subbed before 10k club. also well done for getting this far on yt!

[@jazziiRed]

Thank you!

[@alancinwolfe111]

I have no plans of concocting complicated redstone contraptions myself, but the knowledge of the extent of what the |-_-| can do ought to be somewhat useful 👍

[@c0smicsands]

Disclaimer: It cannot see your pain

[@SETHthegodofchaos]

Great video. Also, the humor. Top notch 👌

[@mallusaih]

my theory about the shulker box activating twice is that it is activated once for the actual opening / closing function and once for the visual changing of the block

[@hyper_lynx]

I think really the box is updating its shape over and over (think of what happens if you stand on one as it is opening) and the observer pulses slowly enough that it happens to only go off twice

[@mrmurpleqwerty4838]

Nobody: Almost every Natural Block: When it grows. Coral: When it dries up and dies.

[@OGwold]

Beds: An observer will notice when a bed is occupied or not. It sends an output when a player, a villager, or a villager child sleeps, and when they get out of bed. It will not trigger if the child jumps on the bed, nor if a cat sleeps on it.

[@messier82]

Saw some of your videos and I love them! Keep up your beautiful work! :D

[@jazziiRed]

Thanks!

[@foryoutube3133]

I almost never make comments, and more so, don’t play minecraft for some time. But you have made me make an exception. Extremely underrated, hopefully will see you with at least 100k subs in some time soon. Good luck mate

[@jazziiRed]

I appreciate it!

[@danielkostenko8189]

Congrats on 2k subs! :)

[@jazziiRed]

Thanks!

[@duckfaceguy]

Beautiful! Thanks for the video. Really helped me in a circuit

[@jackhaley3210]

Damn I hope this guy catches on big time. What a quality channel

[@ruslanart8734]

for those wondering, the music at 4:20 is Mozart symphony number 38 in d major and I believe the 3rd movement

[@seeit360]

Technical: The observer updates when the block permutation changes to a different permutation within that block. Knowing this allows you to understand different parts of blocks. A chest is a block with an entity lid, and observers cannot see entities. So what seems to be the same block is just clever switching, like falling sand. My favorite block that reveals this is the enchanting table which has a block body and an entity book. Entities are not visible in menus or item frames so when you examine the enchanting table in one of those occurances, it's missing its book. But this is changing. Slowly. Notice the skulk sensor, which has moving tendrils in the menu and item frame. That animation is all block, no entity and achieved using permutations of the block. The reason they have not done this with the enchanting table is the Book follows the player, and only entities have this capability.

[@litterbox019]

that intro is gonna conceptualize observer r34 edit: omg the "when it grows"

[@jazziiRed]

Oh no what have I done lol

[@litterbox019]

@@jazziiRed maybe it's fine, the video has only 516 views so far and my comment is very new maybe it hasn't happened yet...

[@moose0095]

I love how as time goes on you can just hear the pain in his voice as he must repeat "when it grows" a hundred times

[@garysochnikoff8942]

Really great video!

[@HiyuMarten]

Thank you so much for this, fantastically edited & presented. Makes me happy that the Minecraft redstone tutorial community is still going strong.

[@Gking10]

Good video, can't wait for when it grows.

[@theqracken4035]

Just found your channel and am already in love. XD

[@jazziiRed]

Thanks!

[@sbananaboi]

That intro was amazing!

[@AU_Player]

Your channel is soo cool, i wonder when it *will grow*

[@JoshAbellSmith]

Most of these could be summarized as... It detects any change in the block ID or block states (visible in the debug (AKA F3) menu), but does not detect changes in NBT data... But then there wouldn't be much of a video, and it does require some technical understanding. This explains, for example, the Campfire, as it has a block state for "lit" but not for items on it. It also highlights one that you missed; when you place/remove a Hay Bale under the Campfire (the "signal_fire" block state). Some others... - Scaffolding and Leaves have block states for how far they are from a support - Bell has "powered" block state, but none for ringing - Redstone Wire has the "power" block state, but the Repeater and Comparator don't - None of the chests have block states for opening Interestingly, the Shulker Box does not have any block states for opening, despite it being detected. I think that might be the only one I can't explain. Nonetheless, nice work putting all of these together! Must have taken quite a while.

[@TheRedSmarty]

Comparators are not always full strength, they just store their signal as block entity data instead of a block state (likely because that was the only way they could work when they were introduced, and they didn't decide to change it with The Flattening of 1.13 like they did Note Blocks). Yeah, Shulker Boxes were weird, might be because their hotbox dynamically changes when opened and closed.

[@JoshAbellSmith]

Right, yes, you're correct about the Comparator @@TheRedSmarty. I forgot about the subtract mode. My bad. (I corrected my original comment.)

[@martitoto9715]

yoo im the 600 sub, im so glad that i found out ur channel is amazing and keep it up!

[@jazziiRed]

I appreciate the support!

[@plumper303]

17:12 Love the reference. :)

[@skeleton8817]

Already knew all of these cases, but still enjoyed watching the video. Your voice is nice and comforting :) #whenitgrows

[@dewaunwarren1]

Thank you, I've been struggling to understand how flying machines work for the longest time. I didn't know observers could detect themselves moving. 👍

[@jalaska007]

|-_-| great work on this, the amount of research, seriously impressive.

[@jazziiRed]

Thanks! |-_-|

[@bjw6877]

Etho pointed out another thing that causes observers to fire: fire blocks. In episode 582 of his letsplay around the 14:16 mark, he shows that a newly lit fire causes observers to randomly fire for a couple minutes or so.

[@moduli7597]

The way of editing this has needs more viewers here seriously

[@idkusername2795]

I just noticed, the observer looks like it’s doing what in Switzerland is known as the Swiss glare, if you see someone do something weird you stare at them like that, and everyone here does it.

[@Draugo]

Observer is like a proud parent, it gets excited when you grow.

[@TacoSlayer36]

Does it detect when you clip a plant with shears? Like when you click on the end of a weeping vine to make it stop growing?

[@jazziiRed]

I just checked, and it does. Good catch! You're the first to accurately find something I missed :D

[@mace1234]

i freaking love your videos

[@rwolterbeek]

Amazing vid! Memorizingly interesting! Only felt myself wondering, does it see when a music disk is done playing instead of it being removed?

[@gdtargetvn2418]

Basically the observer can detect whenever a block changes one of its properties For example, scaffolding has a property called "distance", when you change its value, observer detects that; wall changes its shape, observer detects that as well; note block changes its instruments by placing a block below, observer also detects that.

[@WD_RatLad]

The observer gets very excited when it sees the wood logs stripping.

[@clawrolinelore4674]

Do sponges create a block update and thus get observed when they dry out in the nether? The only way to see would be to place a wet sponge in the nether before 1.15, then update to 1.15 and place something next to the sponge so the sponge updates. I'm pretty sure the observer would detect this but I'm not really sure since there would be no need for Mojang to add that because it already gets detected by placing it. Also observers only look for the change of block states, so doing things like brewing or putting food on a campfire doesn't work because that's part of the block entity. You can check what works by looking at the block in the F3 menu and seeing all of the things that change with the block states.

[@Lattrodon]

I love the thumbnail so much lol

[@TheBcoolGuy]

I don't see it as judgemental. I see it as extremely focused and determined.

[@mac1991seth]

With banner placement, I think the most sane explanation is that the observer "sees" the airblock changing state, such as "placing stuff on the wall" and "placing stuff on the ground".

[@michaelfrey1509]

"Disclaimer, it cannot see your pain" even with context is such an incredibly funny line (8:33)

[@Unpug]

Beautiful video

[@SunroseStudios]

basically, what it's detecting is a change in *block state*. this includes almost anything that changes the appearance of a block, and a few other things. if you can see it change in the "targeted blocK' segment of the f3 menu, the observer can see it too.

[@jazziiRed]

Yes, that is a great way to summarize it.

[@OvercastWarmth]

I think there might be a few extra things the observer can detect that don’t have an associated block state but I could be wrong But it’s kinda funny that this whole video can be summarised as ‘when it changes block state’ Still a great watch though

[@SunroseStudios]

@@OvercastWarmth i don't think so, but we're curious if you know any counterexamples? everything in the video is a block state change (this includes changing what the block even is)

[@TheRedSmarty]

​@@SunroseStudios Shulker Boxes.

[@thepoglin8479]

A dispenser can only act, blind to its surrounding and blind to consequence, to act without reason and without cause is to not act at all. Yet observers know consequence and know reason, to see all and know all is to know beauty and know disgust. It is heaven in the most utilitarian sense

[@danylomusic4624]

Observer detects when you drop a like, when you leave a comment, when you start watching this video, when you return to this video

[@sonicwaveinfinitymiddwelle8555]

6:45 that might be useful for explaining why packing wood too close and leaving logs uncut might cause tree farm not work for noobs

[@twelvethousandths1698]

That propagating pattern with the scaffolding blocks could be very useful!

[@Itemtotem]

great vid, thanks

[@buildermonkey2229]

It does see everything about a block, but it can only see one block in front of it. You are safe from it ... for now.

[@Lampe2020]

The chest etc. probably don't trigger the observer because they are "tile entities", so technically not blocks. Although that would mean that shulker boxes shouldn't trigger them either, sooo…

[@TinyDeskEngineer]

Basically it just detects when the block it's looking at either changes from one block to another, for example, breaking or placing a block, or a sapling growing and turning into a log. Or changing state, for example, blocks like fences, walls, and redstone which connect to other blocks have an individual state for each direction they can connect in, and a change in any of these states will trigger an observer. Things that grow over time, like saplings, or planted crops have a state for what stage of growth. You can see all of the states of a block by looking at it while the debug overlay is active. The observer will only trigger when a block changes, so entities such as falling blocks or item frames will not trigger it.

[@AlbySilly]

Scaffolding and leaves were the most interesting to me, the rest were fairly straight forward since it's just BUD

[@AlbySilly]

I did know about string earlier, it's still super interesting to make a silent pressure plate, but since I already knew about it I didn't mention it

[@Faitorrr]

i thought you had like 100k subs you are amazing :]

[@VenTGM09]

Basically, it detects any changes to BlockState (e.g., Waterlogging, Signal Strength, Collision, Texture; including completely changing the block) but ignores changes to TileState (e.g., Chest Opening). Comparators do the opposite. Instead of BlockState, it's TileState and vice versa, and instead of state change, it's the current state. Some BlockStates also change alongside TileState, so you may get special cases too. Also, you missed Sponge-Drying (Nether [Java and Bedrock] and Desert [Bedrock]).

[@twelvethousandths1698]

This is such a great minecraft channel！

[@notjacob4724]

I have an idea for a video. You make a radio sort of that sends different images on different ticks to machines that can pick up these images. Say it is a 4x4 image, you would have 16 wires that connect to all machines but it can change depending on what tick you let the signal form the wires in therefor giving you a different image.

[@ZerkUWU]

for sponges... In case you put a wet sponge in the nether in front of an observer, will it send two signals? One for putting the block and another for it drying out

[@leorigami8766]

i really love your videos!!! i didn't understand nothing about observers before watching this, but now i will make a watermelon farm!! xD

[@jazziiRed]

Glad I could help!

[@darkener3210]

Nearly very block can be powered and unpowered and it can detect that, what you seeing with the bell is it being powered and then unpowered by the button, thats why it doesnt detect you hitting it manually. Thats also whats happening with the target block, its not detecting getting hit, its detecting being turned on, which happens to be when it gets hit. Also when the falling blocks fall, its not detecting them landing or falling, its detecting the bock in front of them changing to and from air respectively

[@samuels1123]

Basically, any non-continuous block flag changing state or value including the block type. Things that can be found cleanly listed in the F3 menu.

[@fireninja8250]

I unironically liked subscribed and hit the bell

[@jazziiRed]

Thanks and welcome aboard!

[@pigeom32]

I think it would have been a lot easier to say what the observer can't see

[@sinom]

Basically everything that causes a block update. This can be the block completely changing to a different one, like when stripping a log, or when its NBT data changes, like fences changing their state or saplings changing their growth state. Everything in this video falls under those two rules. So it would be a lot more interesting to point out any exceptions to those two rules (if there are any).

[@TheRedSmarty]

Block state changes are not actually the same as block updates, they refer to slightly different things. Also, when you said NBT, you were talking about block properties changing. NBT is not detected. Also, Shulker Boxes don't fit.

[@a.j.outlaster1222]

"There's. Nothing in front of you." "So?"

[@BierBart12]

I wonder if this video will inspire some interesting lock mechanisms An adventure map all about the Observer's birthday

[@Appledirt]

I have one small correction! When you break string attached to a tripwire hook, if you use Shears, it doesn't produce a Redstone signal. Therfore, in that case, the observer would only detect one update, not two

[@StarFried]

this video is only 18 minutes long and yet it felt longer than a lot of 2 hour long videos i have watched

[@TheMilkiestCereal]

I was expecting you to go into the source code of the observer and literally tell us what it actually sees, but awesome video dude!

[@Fireheart318]

17:14 It took me SO long to get that joke but I love it!

[@SkKedDy]

I dont get it 😢

[@vii-ka]

Alternative title: List of block tick updates

[@funimonki4803]

I learned stuff that are off-topic. Such as lighting off the candles, scaffolding changing texture when it has no support, etc.

[@qhgaming8653]

3:26 The most satysfying part of the video

[@K.H.A.Y.A.L.I]

In bedrock edition observed cannot detect 1. Redstone dust shape changes. 2. Leaves when logs are removed or placed next to them. 3. Note block when powered or depowered. 4. Note block when block changes beneath it. 5. When a plant grows without changes it shape naturally.(Gets detected with bonemeal) Well there were 100 of different things that observer couldn't detect before 1.18 but got fixed after the update.

[@purplef0xx]

Can't you make an observer detect the growth of a cactus by placing the observer above the cactus facing its top face, but with an air block between the top of the cactus and the observer? That way the cactus will grow and then instantly break, which will be detected