Lattice

Local couch co-op for Minecraft. Two or more players, each with their own mouse and keyboard, each in their own game window, all on a single PC. No virtual machines, no second computer, no streaming overhead.

Lattice lets every player in the room have their own Minecraft window, using their own set of controls, with nothing leaking between them. When Player 1 types in chat, only their window sees it. When Player 2 opens their inventory and shift-clicks an item, nothing happens on Player 1's screen. It is the same experience you would get from two separate computers, just on one.

What you get

• True per-player input. Player 1's WASD does not move Player 2's character. Player 1's mouse does not drag Player 2's hotbar.
• Per-player HUD. Optional on-screen label, connection indicator, and capture-state dot. Customizable per slot.
• Borderless on capture. Window decorations are stripped automatically when capture is active so the visible frame matches the playable area, and restored when capture toggles off.
• Menus work. Inventories, chat, sign editing, book editing, command boxes, Shift-click, Ctrl+A, modifier keys, and Unicode character input all dispatch correctly per player.
• Multi-monitor aware. Each instance snaps to its own monitor's work area when you set up a multi-display rig.
• Soft-pause toggle. A free mode per instance lets a single player step away and use their PC normally without breaking the other players.

How it works

Lattice comes in two pieces that work together:

1. The mod (this page). A free Fabric mod you install into each Minecraft instance you want to include. It stays quiet in the background until the companion app connects.
2. Lattice Weaver, the companion app. A Windows desktop app that watches every connected mouse and keyboard, asks you which device belongs to which player, and then sends each player's actions to the right game window. It is the heart of the system - the mod does not do anything on its own without it.

Setup is a one-time thing: install the mod into each instance, launch the companion, click each player's mouse and keyboard so the app can tell them apart, and press a key to start playing. From then on, each device only controls its own game window.

Setup

1. Install Fabric Loader for your Minecraft version.
2. Drop Fabric API and the matching Lattice file into each instance's mods/ folder.
3. Give each instance its own player number - add -Dlattice.player=N to the instance's JVM arguments (0 for player 1, 1 for player 2, and so on).
4. Download Lattice Weaver (see Get the companion below) and run it once to enroll your devices.
5. Launch the companion, then launch your game instances.
6. Press End (or your configured toggle key) to start capturing.

A green dot will appear on each player's HUD when their game links up with the companion. From there, just play.

Compatibility

Fabric-only and Windows-only for now. Current compatibility ranges are:

• Minecraft 1.20.1-1.20.6
• Minecraft 1.21-1.21.11
• Minecraft 26.1-26.1.2

Fabric API is required. Mod Menu is optional but recommended so you can reach the in-game config screen.

Get the companion

Lattice Weaver is the Windows companion app that powers the mod. Download lattice-weaver.exe from the official site, or grab it directly from GitHub Releases. Paying customers also get the download in their Polar account after purchase.

A free 45-minute trial is included - active play time only accumulates while at least one game instance is linked and capture is on. Every feature on this page is available during the trial; it is the full app, just time-limited.

Unlock unlimited use

A one-time $14.99 license key unlocks the companion permanently on one PC.

-> See the site for more info.

In-game config

Open the config screen via Mod Menu (or edit config/lattice.properties directly) to customize the HUD, change the capture toggle key, control window-border behavior, and set per-player labels. The screen is fully scrollable so it works on small windows. Everything has a default that works out of the box - you can ignore the config screen entirely until you want to tune something.

Roadmap

• Profile auto-detection by USB port path, so you do not have to re-identify devices every session
• Companion auto-launch of game instances with the right player slot pre-set
• Gamepad / XInput routing per player
• 1.8.9 backport
• Forge / NeoForge support
• macOS and Linux support (long-term - requires a new input backend for each OS)

Source and license

Source is currently closed. All rights reserved. The mod may be freely downloaded and used as published on this page. Issue tracker (link coming with public release).