If you want to play this pre-release, choose the "Latest Snapshot" profile in your launcher. Keep in mind that snapshots are unstable - they can break your world if you are unlucky - keep backups!
Changes in this version: Mobs: - Fixed spider and chicken jockeys only spawning the additional mob - Fixed cods suffocating when touching a solid block from below - Fixed the drowned overlay turning dark blue when wearing enchanted armor - Fixed iron golems spawning inside blocks
Gameplay: - Fixed the density of nether and overworld ore veins being significantly lower in 18w versions - Fixed the swimming state not ending when teleporting or jumping out of water - Fixed moving frosted ice preempting melting even under correct conditions - Fixed not being able to empty buckets against blocks with the state waterlogged - Fixed dispensers with empty buckets removing waterlogged blocks instead of drying them out - Fixed projectiles ignoring collisions for ~1 block after spawned - Fixed the ender dragon respawning when upgrading from 1.12 to 1.13-pre3
Commands & map making: - Fixed /datapack disable only working in the overworld - Fixed inverted tab-suggestions for argument values in entity selectors being suggested even if the typed prefix doesn't include an exclamation mark - Fixed input range entry and limits being reversed in error messages - Fixed the objective minecraft.used only ticking up when placing a block from a stack of 2 or more items
Tech stuff: - Renamed a lot of internal IDs to be more consistent with the game
Stability: - Fixed the faulty netty-4.1.9.Final release causing players to be kicked from servers - Fixed malformed JSON as 'name' value for 'show_entity' hoverEvent causing a crash - Fixed opening the player inventory with visible recipe book after using beacon causing a crash