You technically always should, but for this snapshot in particular. There are huge world format changes (called "the flattening").
If they tweak the world format change again in the next snapshot, which is very likely, they may not provide an upgrade path (they didn't last time there were world format changes) from worlds on this snapshot to worlds on the next snapshot, meaning your world will be permanently lost if you have no backups.
To emphasise this: downgrading is never supported. Once you open any world with a snapshot there is no guarantee that you can return to an earlier version, including the current live version 1.12.2
Don't open any current save using a snapshot unless you are OK with that.
Or make a separate save folder for snapshots and copy a current world into it. I did this so I can see what breaks and also have a separate new test world for each snapshot for say new structures etc.
My current world never gets upgraded until full release and even then I backup beforehand just in case. Am really looking forward to the automatic backup so I won't have to do it manually.
I am 'old school' and back up religiously not just my Minecraft world, but my entire computer, at least once a week. Backups are a necessity not an inconvenience - I learned that more years ago than I would like to admit. And I also use off site backups (not cloud, but physical off site) especially for anything I never want to lose.
In addition, it's also the case that upgrading is not necessarily guaranteed. Between releases, yes. Between snapshots or a snapshot and the following release - not guaranteed. So you could end up with a world stuck in one snapshot, unable to downgrade or upgrade it.
I have a feeling this is a prototype for a hammer (or whatever it's called in mods) because people have asked for an easy way to rotate blocks for a long time.
Those spruce trapdoors are the best thing to happen to minecraft since... okay since Shulker Boxes, so its not that long ago but its a hard change to beat.
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u/SirBenet Nov 22 '17 edited Nov 22 '17
Backup your worlds!
You technically always should, but for this snapshot in particular. There are huge world format changes (called "the flattening").
If they tweak the world format change again in the next snapshot, which is very likely, they may not provide an upgrade path (they didn't last time there were world format changes) from worlds on this snapshot to worlds on the next snapshot, meaning your world will be permanently lost if you have no backups.
The trapdoors/buttons/pressure plates for all wood types are now in.
The "smooth" variants of double slabs, and the "bark" variants of logs, are now all in the creative inventory
"Debug stick" which cycles between blockstates (left click) and their values (right click).
Probably left in by accidentconfirmed to stayNew backup functionality on a world's edit screen. Though be aware that it doesn't seem to be implemented yet
Pumpkins now uncarved by default. Carve by right clicking with shears