CHANGES IN 18W20A
Sleeping in creative mode is now more comfortable
All worlds created in older snapshots should finally be openable again
Fire no longer spreads everywhere
Lots of bugfixes
FIXED BUGS IN 18W20A
MC-9620 - F1 and open chat makes hotbar appear
MC-116928 - Command block and spawner minecart data fixer not working correctly
MC-121743 - Feedback of some commands uses OS locale for formatting decimal numbers
MC-122331 - Shield with banner has broken colors
[MC...........] - 40 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!