🔷 Before You Click

Preview the consequences before you act.

Before You Click is a fully client-side Fabric mod for Minecraft 1.21.1 that shows what may happen before you break a block, place a liquid, or trigger an explosion.

Simply hold Left Alt to display a context-sensitive preview. The simulation is visual only and never modifies the real world.

📸 Screenshots

💧 Liquid Flow Preview	⛏️ Falling Block Preview
🔗 Support Chain Preview	🛤️ Rail Dependency Preview

⛏️ Break Preview

See which blocks may be affected before breaking the targeted block.

The preview supports:

Unsupported blocks
Chained support failures
Sand, gravel, concrete powder, and anvils
Modded FallingBlock subclasses
Doors, beds, and tall plants
Torches, ladders, buttons, and levers
Redstone dust, repeaters, and comparators
Flat, curved, and ascending rails
Horizontal and vertical scaffolding
Pointed dripstone
Waterlogged blocks

Many modded support-dependent blocks can also work automatically through Minecraft's standard BlockState#canPlaceAt placement rules.

The simulation temporarily treats blocks queued for removal as air during bounded support checks. This allows dependency chains to be previewed without modifying the actual world.

💧 Liquid Preview

Preview the likely result before placing water, lava, or liquid from an entity bucket.

The mod can visualize:

Source placement
Waterlogging
Horizontal spreading
Vertical drops
Nearby pits and ledges
Blocked placement
Water and lava reaction points
Water evaporation in ultrawarm dimensions
Fish buckets and other entity buckets

The liquid simulation is intentionally bounded and approximate, allowing it to remain lightweight and responsive.

It does not reproduce Minecraft's complete fluid tick scheduler, infinite-source rules, or every possible complex terrain interaction.

💥 Explosion Preview

Preview dangerous interactions involving:

TNT
Beds in explosive dimensions
Charged Respawn Anchors
End Crystals
TNT chain reactions
TNT and End Crystal combinations

The explosion preview can display:

Estimated blast areas
Explosion wave boundaries
Estimated affected blocks
Detected explosion events
Chain progression
Player danger status

Large explosion chains are calculated gradually across multiple client ticks to reduce freezing and sudden frame drops.

TNT normally requires flint and steel or a fire charge to display a preview. This can be changed with the previewTntWithoutIgniter configuration option.

Explosion results are estimates. Actual destruction depends on blast resistance, shielding, ray exposure, entity state, and Minecraft's internal explosion calculations.

✨ Specialized Rendering

Different preview types use visuals designed specifically for their purpose:

Color-coded block outlines
Simplified full-body bed outlines
Shape-following rail overlays
Liquid flow routes and reaction markers
Explosion wave surfaces
Context-sensitive HUD information

Preview geometry is cached and rebuilt only when the result changes.

Moving the camera does not restart an unchanged simulation. Releasing the preview key, changing targets, changing held items, or leaving the world clears temporary preview data.

🎮 Controls

The default preview key is:

Left Alt

Hold the key to display the preview.

The key can be changed from Minecraft's Controls menu.

The configuration also supports toggle mode, allowing the preview to be enabled and disabled with a single press.

⚙️ Configuration

The configuration file is created automatically at:

config/beforeyouclick.json

Available settings include:

Hold or toggle activation
Individual preview categories
HUD visibility
Rendering options
Refresh rate
Simulation limits
Explosion chain limits
TNT preview without holding an igniter

Important default values:

{
  "toggleMode": false,
  "previewTntWithoutIgniter": false
}

🖥️ Client-Side Only

Before You Click is completely client-side.

No server installation required
No custom network packets
No server-side classes
No world modifications
Works on vanilla and Fabric servers
Other players do not need the mod
Automatically recognizes modded falling blocks
Tested with Sodium
Tested with Iris and shaders

Unsupported or heavily customized modded blocks fail safely instead of crashing the game.

⚠️ Known Limitations

The previews are estimates and may not always match the final result perfectly.

Complex natural terrain can cause small differences in liquid routing.
Liquid simulation is not a complete copy of Minecraft's fluid tick scheduler.
Explosion destruction depends on resistance, shielding, ray exposure, and Minecraft's internal calculations.
Long TNT chains may display their waves and detected events without showing every affected-block overlay.
Blocks controlled by scheduled ticks, block entities, or custom server logic may require dedicated compatibility support.
Item frames and paintings are entities and are not included in break-chain previews.
Piston movement and complete redstone-state simulation are not included in version 1.0.0.

📦 Requirements

Minecraft 1.21.1
Fabric Loader 0.19.3 or newer
Fabric API 0.116.14 or newer
Java 21

📥 Installation

Install Fabric Loader for Minecraft 1.21.1.
Install Fabric API.
Place beforeyouclick-1.0.0.jar inside the Minecraft mods folder.
Launch the game.

The mod does not need to be installed on the server.

🔗 Source Code

The project is open source:

GitHub — Before You Click

Think first. Preview the result. Then click.