This is BuildBattle

For Minecraft 26.3, Fabric Loader 0.19.5+, Fabric API.

New since 4.5.0

• Licensed accounts only. The mod opens only on a licensed Minecraft account, checked online every time the game starts, the way a server checks a player. Without an internet connection the mod can't be played.
• Friends, first step. A new Community section in the side menu with Friends: your own friend code (BB-XXXX) to share. Friend requests, the friends list and the activity feed come in the next updates.
• XP only for real games. A game ended with /cancelgame, or a build with fewer than 16 blocks above the floor, is still saved but earns no XP; such small builds aren't published for rating.
• A taller arena. Builds can now reach 48 blocks high instead of 31.
• Turn builds everywhere. Drag a build with the mouse in My builds, its ratings and the trash.
• Mods from CurseForge pass the mod check. The check asks both Modrinth and CurseForge for every player.
• Respawn anchors no longer explode in the mod's world.
• Shift-clicking the bin in the creative inventory clears everything except the tools item.
• No dropped items are left lying around when a game starts.
• A guest who leaves a duel mid-game no longer leaves mobs behind in their arena.
• A lobby host's game can no longer write impossible ratings or statistics into a guest's save.
• The side menu fits the smallest windows again.

Both players of a duel or duo need 4.6.0. Builds and progress from earlier versions are kept.