Minecraft: Java Edition 20w49a snapshot adds sculk sensor, dripstone biome for 'Caves and Cliffs Update'

Minecraft Caves and Cliffs Update Image
Minecraft Caves and Cliffs Update Image (Image credit: Mojang Studios)

What you need to know

  • Minecraft: Java Edition is the legacy PC version of Minecraft, complete with modding and an impassioned community.
  • The Java Edition tests new features and updates through snapshots, or temporary builds that anyone can try out.
  • The latest snapshot tests new features from the upcoming 'Caves and Cliffs Update,' which is coming Summer 2021.
  • This includes the new dripstone caves biome, as well as the fancy sculk sensor that can detect sound through vibrations.

Minecraft is back with another snapshot for the Java Edition, once again adding and testing new features and changes from the upcoming Caves and Cliffs Update, which is releasing Summer 2021. The new snapshot, dubbed 20w49a, adds two new features for players to try out, as well as a host of technical changes, bug fixes, and more.

The two highlights from this snapshot are certainly the dripstone caves biome, which gives the dripstone blocks introduced in the last snapshot a new home, and the sculk sensor, which can detect sound via vibrations and gives off redstone signals.

Minecraft, one of the Best Games for Kids, continues to grow and evolve over time. With the sculk sensors being added in this update, sound is more important than ever, so make sure you're well-acquainted with one of the Best Headsets for PC Gaming.

The full changelog for snapshot 20w49a (sans bug fixes) includes:

New features

  • Added dripstone caves biome
  • Added sculk sensors

Dripstone caves biome

  • This biome doesn't generate naturally yet since it is designed for the upcoming larger caves. However, if you want to see the biome in the current caves you can create a single-biome world with dripstone caves
  • Contains plenty of pointed dripstone on the floors, ceilings, and small pools of water
  • In some places, you'll find larger stalagmites, stalactites, and columns built from dripstone blocks

Sculk sensors

  • Introducing the bizarre, tendril-filled world of sculk – prepare for sculk sensors to creep you out with their unique ability to detect vibrations nearby
  • A vibration is anything that causes physical motion; if you are careful, there are some motions that are undetectable to sensors by sneaking
    • These sneak-friendly vibrations currently include walking, falling to the ground, or throwing/shooting projectiles
  • Sculk sensors will not listen to vibrations that are directly created by other sculk sources
  • When a vibration is detected, a signal is sent from the source location to the sensor at a speed of 1 game tick per block
    • Other vibrations cannot be detected by a sensor when a signal is already traveling to it
    • When the signal has arrived, the sensor will be activated for 40 game ticks (approximately 2 seconds)
    • While activated, the sensor cannot detect other vibrations
  • Sculk sensors can detect vibrations in an 8 block radius around it
  • The efficient tool to mine sculk sensors is the hoe
  • They can be waterlogged

Redstone emission

  • Sculk sensors emit a redstone signal when they are activated
  • The strength of the redstone signal is inversely proportional to the distance the vibration signal traveled
    • This means that the closer the vibration is, the stronger the Redstone signal is
    • The output is also scaled based on the sculk sensor's radius, so it can reach the max redstone signal strength when the vibration is 0 distance away (directly on top of the sensor)

Vibration frequences

  • Sculk sensors have a unique interaction with comparators
  • Each vibration in the game falls under a certain frequency value, and this value can be measured with a comparator
  • With the right contraption, this allows you to detect when a certain action has occurred nearby
  • Here is a list of actions and their corresponding frequencies:
    • Step - 1
    • Flap - 2
    • Swim - 3
    • Elytra Free Fall - 4
    • Hit Ground - 5
    • Splash - 6
    • Wolf Shaking - 6
    • Projectile Shoot - 7
    • Projectile Land - 8
    • Start Eating - 7
    • Finish Eating - 8
    • Hit Entity - 9
    • Add Item To Armor Stand - 9
    • Open Block - 11
    • Close Block - 10
    • Switch Block - 11
    • Unswitch Block - 10
    • Press Block - 11
    • Unpress Block - 10
    • Attach Block - 11
    • Detach Block - 10
    • Open Container - 11
    • Close Container - 10
    • Dispense Failed - 10
    • Use Flint And Steel - 12
    • Place Block - 12
    • Destroy Block - 13
    • Place Fluid - 12
    • Pickup Fluid - 13
    • Cast Fishing Rod - 15
    • Reel-In Fishing Rod - 14
    • Extend Piston - 15
    • Contract Piston - 14
    • Explosion - 15
    • Lightning Strike - 15

Wool occlusion

  • Wool has a special interaction with sculk sensors
  • If a wool block is in the way of a vibration source, the sensor will not be able to detect it

Technical tidbits

  • Sculk sensors have a cooldown period of 1 tick after being placed or after deactivating
  • During this short cooldown period, it cannot detect vibrations. This is to prevent it from activating itself when a contraption it is powering is being unpowered. Feedback is welcome on this point!


  • The fullness of a bundle now shows up regardless of whether advanced tooltips are on or off
  • Stalactites and stalagmites merge if the tips are next to each other unless you press shift while placing

Technical changes

A new game event system has been implemented to support Sculk Sensors detecting vibrations World height-related values are now exposed for customized worlds Removed the


server setting Added


block tag. Anything in this tag will occlude vibrations, and inherits


tag entries by default New particle types:




A new game event system has been implemented to support Sculk Sensors detecting vibrations

Game events

  • This system has been developed to identify when certain in-world actions are happening in nearby chunks, particularly so the new sculk sensor can detect these events as vibrations
  • The following is a list of the initial game events:
    • minecraft:step
    • minecraft:swim
    • minecraft:flap
    • minecraft:elytra_free_fall
    • minecraft:hit_ground
    • minecraft:splash
    • minecraft:projectile_shoot
    • minecraft:projectile_land
    • minecraft:entity_hit
    • minecraft:block_place
    • minecraft:block_destroy
    • minecraft:fluid_place
    • minecraft:fluid_pickup
    • minecraft:block_open
    • minecraft:block_close
    • minecraft:block_switch
    • minecraft:block_unswitch
    • minecraft:block_attach
    • minecraft:block_detach
    • minecraft:block_press
    • minecraft:block_unpress
    • minecraft:container_open
    • minecraft:container_close
    • minecraft:explode
    • minecraft:armor_stand_add_item
    • minecraft:wolf_shaking
    • minecraft:dispense_fail
    • minecraft:fishing_rod_cast
    • minecraft:fishing_rod_reel_in
    • minecraft:piston_extend
    • minecraft:piston_contract
    • minecraft:flint_and_steel_use
    • minecraft:eating_start
    • minecraft:eating_finish
    • minecraft:lightning_strike


  • There are also game event tags that come with this and can be modified by data packs. They can be found under data/minecraft/tags/game_events
    • vibrations Determines which game events are considered vibrations by the Sculk Sensor. Currently, all added game events are in this tag by default
    • ignore_vibrations_stepping_carefully Which game events should be ignored by the Sculk Sensor when the source of the event is sneaking
  • The following game events are in ignore_vibrations_stepping_carefully by default:
    • minecraft:step
    • minecraft:hit_ground
    • minecraft:projectile_shoot



Zachary Boddy
Staff Writer

Zachary Boddy (They / Them) is a Staff Writer for Windows Central, primarily focused on covering the latest news in tech and gaming, the best Xbox and PC games, and the most interesting Windows and Xbox hardware. They have been gaming and writing for most of their life starting with the original Xbox, and started out as a freelancer for Windows Central and its sister sites in 2019. Now a full-fledged Staff Writer, Zachary has expanded from only writing about all things Minecraft to covering practically everything on which Windows Central is an expert, especially when it comes to Microsoft. You can find Zachary on Twitter @BoddyZachary.