https://www.minecraft.net/en-us/article/minecraft-snapshot-20w17a 
NEW FEATURES IN 20W17A

• Added an Entity Distance scale option ranging from 50% to 500%
• Difficulty and game rules can now be changed from "Create World" screen

CHANGES IN 20W17A

• Improved Smithing Table UI
• Ruined Portals now spawn less frequently
• Renamed "Soul Fire Torch" and "Soul Fire Lantern" to "Soul Torch" and "Soul Lantern"
• Tweaked Bastion Remnant loot
• Walls now create posts under more things, like pressure plates and banners
• The "Singleplayer" button will jump directly to "Create World" screen if there are no worlds to select

TECHNICAL CHANGES IN 20W17A

• Chat component style can now select font
• Block storage format in chunks slightly changed to speed up various tasks (rendering, pathfinding, world generation, etc)
• Full range of Unicode characters is supported (some may know what that means ????)
• Added the attribute command

WORLD SAVE FORMAT

• Saving level.dat now uses randomly-named temporary files (instead of using level.dat_new every time)
• player/*.dat are now saved in a way similar to level.dat (including leaving .dat_old files)

https://discord.gg/2gxSqWu - 마인크래프트 개발자 디스코드