In this snapshot, we're adding support for custom world settings and custom dimensions. This is an early release to hear your feedback about this feature - do note that this support is considered experimental and unsupported. Any custom world settings may change from one snapshot to the next, and worlds using custom settings will be clearly marked as experimental in your worlds list.

New Features in 20w21a

Added the ability to toggle redstone wire between a cross and a dot
Added import/export world settings functionality
Added a new disableMultiplayer command line option - when used, the Multiplayer button is disabled
Added a new disableChat command line option - when used, receiving and sending online chat is disabled

Redstone Toggle

When right clicking a single piece of redstone, it toggles between a the cross and the dot
A dot of redstone will not power its surrounding blocks

Changes in 20w21a

Piglins no longer walk around when admiring gold
If you hurt a piglin while it is admiring an ingot, the ingot will now disappear
Increased the chance of ores to generate in the Basalt Deltas to balance against the reduced amount of Netherrack in this biome
Lily pads are now considered junk fishing loot rather than treasure
Updated logos for Mojang Studios and Minecraft
Temporarily removed structure settings from flat level preset strings (workaround: use import/export settings functionality)

Technical Changes in 20w21a

Added the ability to control the height of the spreadplayers command
Added custom worlds and custom dimensions

Commands

`spreadplayers`

Added an optional argument to specify maximum height. New syntax: spreadplayers <center> <spreadDistance> <maxRange> [under <maxHeight>] <respectTeams> <targets>

maxHeight - Specifies the maximum height for resulting positions

`locate`

Structure names are now specified as lowercase

Custom Worlds

Added experimental support for new custom worlds
Edit world screen now has an option to export world settings to a JSON file
During world creation you can import previously exported world settings
A bunch of new parameters are exposed, but marked as experimental, meaning you can play with them, but there is no guarantee that any of them will continue working (even in the next snapshot!)
Flat level preset string lost structure settings (they are now stored in a common format for all worlds), we will restore some form of this functionality soon
Buffet world can no longer be created from server.properties, flat level settings changed a bit; better support for custom world creation on the server is coming soon

Fixed bugs in 20w21a

MC-97247 Map making sound uses equipment sound subtitle
MC-97507 Using item which modifies the held item shows "Gear equips" subtitle
MC-107103 Trying to interact with entity 3 or more blocks away without seeing its eyes only interacts client-side
MC-113068 Zombie banging on door subtitle is called "Block broken"
MC-123155 When any non-player entity enters an End portal the obsidian platform is not regenerated and the entity can fall into the void
MC-147516 Hostile mobs will sometimes stop attacking/following their target when directly next to it
MC-166292 Subtitle from foxes eating chorus fruit: "Player teleports"
MC-169764 Fish flopping sound shows 'Footsteps' subtitles
MC-170930 Nether Sprouts item not visible when held in the hand in first person
MC-172090 Piglins would rather hold a golden item instead of a crossbow
MC-172207 Parrots don't imitate hoglins, zoglins and piglins
MC-172255 Piglins immediately dismount any entity that they are riding
MC-177075 Taking product out of stonecutter produces no subtitle
MC-177088 Polar bear step sound does not have subtitles
MC-177438 Turtle egg's name inconsistently capitalized across different subtitles
MC-177830 Blackstone and basalt prevent Ancient Debris and other Nether ores from generating
MC-178130 Zombie Villagers are called "Zombie" in some subtitles
MC-178212 Nether planks, their variants, and hyphae are harder than stems
MC-178298 Ancient debris and nether gold ore can't generate in Basalt Deltas
MC-180257 Crash when setting LodestonePos of compass to something other than NBT compound
MC-180852 There is no space on the beacon's secondary power effects in the UI
MC-181270 Trying to open old worlds (in Region format?) without version information in snapshots does not show warning screen
MC-181298 Game crashes when trying to generate a nether biome superflat world with ruined portals
MC-181463 The buttons are not selected in the right order using Tab in the new world creation menus
MC-181499 Buckets cannot be emptied into a source block, but still produce a sound when trying
MC-181511 Chunks with redstone are removed
MC-181522 Chunks that haven't been explored since 1.13 are resetting
MC-181611 Vindicators stop attacking you when they are standing really close to you
MC-182514 15 Block States per SubChunk Limit during World Upgrade
MC-182743 Wither skeletons don't spawn inside of wither roses
MC-182912 Piglins still do not change their current crossbow for a new enchanted one
MC-183249 Carving Mask BitSets created for lower chunk statuses
MC-183786 Named seeds that are not numbers are not being recognized

Minecraft Snapshot 20w21a