We're getting ready to do pre-releases soon and we're working hard to fix bugs.
A full changelog for the Snapshot can be found on Minecraft.net.
Note from ProfMobius via reddit:
If you can hold until tomorrow, 18w19b will be able to open all the worlds without wiping them. Sorry for the stress generated.
CHANGES IN 18W19A
- Due to changes in world generation, worlds from previous snapshots will no longer work
- All undead mobs now sink
- Skeleton Horses are rideable underwater
- Updated biomes to have new fancy names
- Seagrass now generates in underwater caves
- New sounds for Conduit and Beacon
- Phantoms are now extra flappy
- Improved the upgrade paths from old versions
- You can now copy the output of the
/seedcommand- Updated the credits list
- Maybe some other stuff?
- Fixed a couple of bugs
FIXED BUGS IN 18W19A
- MC-7908 - Spawning underwater / In the middle of an (lava) ocean
- MC-86016 - Some Mojang staff not mentioned in credits.txt
- MC-121285 - Crash on start when resolution is changed in profile
- MC-121636 - Server commands available in singleplayer with weird/bad effects
- MC-121661 - Typing /help + unavailable command returns "unexpected error" message
- [MC-..........] - 96 more bugs
To get snapshots, open your launcher and go to the "launch options" tab. Check the box saying "Enable snapshots" and save. To switch between the snapshot and normal version, you can find a new dropdown menu next to the "Play" button. Back up your world first or run the game on in a different folder (In the "launch options" page).
Please report any and all bugs you find in Minecraft to bugs.mojang.com.
Snapshots can corrupt your world, please backup and/or run them in a different folder from your main worlds. 1.13 will have a lot of experimental snapshots that may break everything and smell funny. This may be one of those snapshots. This is what happens when Mojang are changing all the things!
Share your thoughts on how 1.13 is shaping up in the comments below!