BuildLens

BuildLens is a client-side Fabric mod for Minecraft 26.2 that helps you build with vanilla blocks. No additional items, blocks, or server mods required.

• PistonLens: Hold the inspection key while looking at a retracted piston to preview its extension. Accounts for slime, honey, side connections, the push limit, and blocks destroyed by movement. Blocks moved through sticky connections are highlighted in purple; confirmed obstacles appear in red.
• BeforeBreak: Highlights supported neighboring blocks that would lose their support if you removed the targeted block. Supports torches, redstone torches, redstone dust, repeaters, comparators, levers, buttons, ladders, rails, and bamboo.
• Optional protection mode: Stops you from breaking a block when a support consequence is detected. A separate confirmation key allows normal breaking of the currently confirmed block.

Both modules can be toggled independently. Keybindings, colors, and transparency are configurable. English and German translations are included.

Previews use available client-world data and vanilla rules. Piston retraction, complete redstone sequences, and chain reactions are currently outside the preview’s scope.