Java Edition 16w20a

16w20a is the first snapshot for Java Edition 1.10, released on May 18, 2016, which adds bone, magma, and nether wart blocks; husks and strays as zombie and skeleton variants, respectively; polar bears; and fossils that spawn underground.

Blocks

 * Bone blocks
 * Crafted by filling a 3×3 square in the crafting table with bone meal.
 * Can be crafted back into 9 bone meal.
 * Found underground in desert and swamps as part of fossils.


 * Magma blocks
 * Found in the Nether, generating 4 veins per chunk between y=27 and y=36.
 * It has a similar frequency to blocks like andesite in the Overworld.
 * Crafted using four magma cream.
 * Mobs and players take damage every second while touching it, similar to a cactus.
 * Unlike cactus or fire, this block doesn't destroy items that touch it.
 * If the player is sneaking, wearing Frost Walker–enchanted armor, or under the effect, it does not take damage.
 * If the player dies by standing on it, a new death message will appear: "player discovered that floor was lava".
 * If the player dies by the block, but after being damaged by a mob or player, the death message will be: "player walked into danger zone due to entity".
 * Removes water blocks on top when randomly ticked.
 * It produces smoke particles under the rain.
 * It emits as much light as it receives from other sources.
 * e.g. A magma block next to a torch will emit light at level 13, as that was the light level it received from the torch.
 * If the torch were to be removed then it will search for the next brightest source of light; if no source is found then it will not produce light.


 * Nether wart blocks
 * Crafted by filling a 3×3 square in the crafting table with nether wart.
 * It cannot be crafted back into nether wart.
 * It is broken by flowing water or lava, like most plants are.


 * Red nether bricks
 * Crafted by placing a 2×2 checkerboard of 2 nether brick and 2 nether wart in a crafting table.


 * Structure voids
 * Used for the structure block to keep the blocks in that location.
 * Intended to be a replacement for the function barrier blocks used to convey, so they can form part of the structure itself.
 * They are invisible and have a small hitbox.
 * They are only visible when using the feature in (save) structure void.
 * Allows for empty spaces in a structure.
 * Unlike air, it will not overwrite blocks where it is loaded.
 * Example: If the player loads a 2-block-high structure with air at the top and a structure void at the bottom into a 2-block-high area of stone, the top block will become air but the bottom will stay stone.

Items

 * Spawn eggs
 * Added cat egg: Light brown with brown spots.
 * Added donkey egg: Dark brown with light brown spots.
 * Added elder guardian egg: Light yellow-white with purple spots.
 * Added husk (new zombie variant) egg: Brown with cream colored dots.
 * Added mule egg: Dark brown with black spots.
 * Added polar bear (new neutral mob) egg: White with gray dots.
 * Added skeleton horse egg: Brownish-green with light gray dots.
 * Added stray (new skeleton variant) egg: Dark gray with light gray dots.
 * Added wither skeleton egg: Black with dark gray spots.
 * Added zombie horse egg: Dark green with light green spots..

Mobs

 * Husks
 * 80% of zombies spawned above ground in desert biomes, and their variants, will be husks.
 * All spawns where the zombie does not have a view of the sky will be normal zombies or zombie villagers.
 * Behaves mostly like a regular zombie.
 * Its  tag is 6.
 * Does not burn in sunlight.
 * Can spawn as a baby or as a chicken jockey.
 * Applies 7 seconds of hunger when attacking in Easy, 14 in Normal and 21 in Hard difficulty.
 * Visually 2 pixels taller than zombies, but has the same hitbox.


 * Polar bears
 * Adults and cubs spawn randomly as passive mobs in ice plains, ice mountains, and ice plains spikes.
 * When hit, the adults will attack the player, the cubs will run away (very fast, similar to baby zombies).
 * Additionally, adults will always attack the player when their cubs are around.
 * Can swim faster in water than the player.
 * Cubs will follow their parents.
 * Drops 0–2 raw fish (75% chance) or 0–2 salmon (25% chance), each increased by 1 per level of Looting.


 * Stray
 * 80% of skeletons spawned above ground in ice plains biomes, and their variants, will be strays.
 * All spawns where the skeleton does not have a view of the sky will be normal skeletons.
 * Spiders spawned in cold biomes have a chance of having a stray riding it.
 * Acts mostly like a regular skeleton.
 * Its  tag is 2.
 * Drops are the same as skeletons, but also have a 50% chance to drop 0-1 tipped arrow of when killed by the player. With looting, chance increases to $2×level+1/2×level+2$.
 * Shoots Tipped Arrows of Slowness (0:30) at the target.

World generation

 * Fossils
 * Generates 15–24 blocks underground in deserts, swamplands, and their variants. Each chunk has a $1/64$ chance of generating a fossil.
 * Composed of bone blocks and some coal ore, arranged as to resemble the skulls and spines of giant extinct creatures.
 * There are 4 variants of the skull, and 4 variants of the spine sections.

Command format

 * NBT tags
 * : Determines the kind of zombie a specific zombie is.
 * 0: default, 1-5: villager, 6: husk.
 * This tag, in effect, unifies the characteristics of being a zombie, a specific zombie villager and a husk into a single variable.
 * Intended to replace the  and   tags.
 * These tags are kept for backwards compatibility, but no newly generated entities have them.


 * Sound events
 * Added.
 * Added.
 * Added.
 * Added.
 * Added.
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 * Added.

General

 * Debug screen
 * toggles the visibility of chunk borders around the player.
 * Shows a blue outline for the chunk the player is currently in and a yellow outline for individual air blocks in the vicinity of the chunk.
 * The blue outline in particular, will outline the chunk horizontally on top of the solid blocks on the ground.
 * The outlines extends arbitrarily up, but ends at bedrock level.


 * Loot tables
 * A new tag  for the   function.
 * It determines the maximum amount of mob drops the player can expect to receive when using the looting enchantment of any level.


 * Options
 * A new 'Auto-jump' toggle has been added, which automatically makes the player jump when running towards a one block tall obstacle.
 * Enabled by default, can be disabled in Options.


 * Particles
 * A new  particle has been added.
 * Appears underneath gravity-affected blocks that are generated or placed suspended in midair.
 * Does not apply to dragon eggs.

Blocks

 * End stone bricks
 * Are no longer craftable.


 * Structure blocks
 * Are now available in item form; can be given or summoned.
 * Similarly to command blocks, its placement, destruction, and modification are restricted to opped players in creative.
 * Now comes with an integrated GUI and new textures.
 * Has four modes:
 * Save - build structure in world, tell the block where it is and it saves it to file.
 * Load - loads saved structure files, replacing blocks with saved blocks except for structure void blocks.
 * Corner - for automatic size calculation.
 * Data - for chest markers and other blocks that require data (default).
 * Structures are limited to a size of 32 blocks in each direction.
 * The coordinates used by the blocks are relative to themselves.
 * When in use, it shows the outline of the structure it relates to in white.
 * Can rotate and mirror structures before they are placed.
 * Small red and blue cubes can be displayed in the selection area.
 * Blue is for air blocks, red is for structure void blocks.
 * Save and Load structure blocks can be activated by redstone.
 * The game protects against maps saving arbitrarily massive amounts of data to disk.
 * Display a name tag above them indicating their mode and structure name.
 * New NBT tags
 * : Whether or not the structure block is currently being powered with redstone.
 * : Whether or not the bounding box of the structure is being outlined.
 * : Whether or not air blocks are indicated within the structure.

Items

 * Firework rockets
 * Recipe now produces three rockets rather than only one.

Mobs

 * Endermen
 * Can now rarely spawn in the Nether with a $1/153$ rate.
 * Compared to $100/153$ for zombie pigmen.
 * Can now naturally pick up netherrack.


 * Magma cubes
 * Spawn about twice as often in the Nether.
 * The rate is now $2/153$, compared to $1/151$ before.


 * Zombies
 * The Zombie Generic Villager is removed, due to the new zombietype tag.

World generation

 * Caves
 * No longer turn adjacent sand blocks in the ceiling into sandstone when generating.


 * Ice plains and variants
 * Don't spawn any other passive mobs than rabbits and the new polar bears anymore.
 * Also have a lower chance of spawning passive mobs during world generation than other biomes (7% versus 10%).


 * Mesas, including all variants
 * Terracotta and the dyed forms of terracotta no longer generate more than 15 blocks deep, if the mesa is more than 15 blocks above sea level.
 * In addition to the normal 2 veins of gold ore below Y=32, attempts to generate 20 veins between Y=32 and Y=79.
 * Generate the new type of mineshafts, described below.


 * Mineshafts
 * New mineshaft type that generates in mesa biomes (including all variants).
 * Placed so that the midpoint of the structure is near sea level, rather than so that the top is 10 blocks or more below sea level.
 * Uses dark oak wood for wooden structures.
 * New NBT tag  on mineshaft structure pieces to indicate the type. 0 is the traditional mineshaft, 1 is the new mesa mineshaft.
 * Features generate differently if above ground (i.e. the sky light where they generate is 8 or more). This is not dependent on mineshaft type.
 * Cave spider spawners no longer generate if sky light is 8 or more.
 * Various wooden pieces no longer generate if the block above is air and/or if sky light is 8 or more.
 * Rails in corridors are more complete if sky light is below 8.
 * 90%, versus 70% in 1.9 and in above-ground corridors.


 * Plains and sunflower plains
 * Now have some trees in 5% of its chunks ($1/3$ large oaks, $2/3$ normal oaks).


 * Villages
 * Village structures are no longer restricted by biome boundaries.
 * Meaning that a village that starts in a valid biome can now spread into an adjacent invalid biome.
 * Now generate in taigas (but not variants).
 * They are made with spruce log.
 * Savanna villages are now made with acacia wood instead of oak.
 * In savannas, acacia logs replace cobblestone in all structures except churches.
 * Paths no longer generate below sea level, and in non-desert villages they are made with different material depending on the existing terrain.
 * If replacing grass blocks, the path is made from grass path blocks.
 * If replacing water or lava, the path is made from planks.
 * Otherwise, the path is gravel on top of cobblestone (including bridges across ravines).
 * Sandstone paths still always generate in desert villages.
 * They have a 2% chance of being a zombie village, determined by  NBT tag in.
 * All generated villagers are instead zombie villagers.
 * There are no doors or torches in the village.

Command format

 * NBT tags
 * now works for all entities, not only armor stands.
 * A mob in midair affected by it, will still respond to knockback by moving horizontally.
 * Although the AI will not permit any mob to move on their own, horses and pigs ridden by the player, will move normally.
 * Very similarly, boats in the air ridden by the player, will move as if they were in water.

Gameplay

 * Huge mushrooms
 * Huge mushrooms have a 1⁄12 chance of generating twice as tall as normal.
 * These new mushrooms, which can be up to 13 blocks tall, can appear during world generation or by being planted by the player.

Fixes

 * More fixes
 * Fixed some broken uses of relative coordinates.

Video
Video made by slicedlime:

Trivia

 * 16w20a was previously removed from the launcher for some time, but was added back in September 2018.