⚠️ IMPORTANT — REQUIRED DEPENDENCIES

Justify Test Chambers requires Justify API and Justify Portal Gun.

Download Justify API · Download Justify Portal Gun

Install matching release versions of all Justify mods. Fabric API is also required when using Fabric.

Justify Test Chambers

Create, share and play Portal-style test chambers, with an in-game editor, community maps, solo and co-op puzzles, and a Portal 2-inspired interface.

Justify Test Chambers brings a complete chamber-building workflow to Minecraft. Build a puzzle with Justify Portal Gun's portals, cubes, gels and mechanisms, set its rules, test your solution, and share it with other players.

You can also browse the community catalogue, download someone else's chamber, and start solving puzzles straight from the game.

Chamber Editor

Create a chamber from a room preset or choose your own dimensions. Once the room is ready, you enter Creative mode with a building kit and can start building immediately.

The editor lets you configure:

• Starting position and inventory
• Finish point and checkpoints
• Solo or two-player co-op
• Chamber title and description
• Gameplay rules and background music

The editor is available through the Aperture icon in the pause menu. Chamber generation and file transfers display a progress bar and percentage.

Playtesting and Progress

Use Save and playtest to try your chamber in Adventure mode. Each playtest runs in a separate copy, keeping your building project ready for further edits.

Checkpoints update the player's respawn position, and reaching the finish displays the completion time. You can save an unfinished playthrough and continue it later from your library.

Community Test Chambers

The in-game catalogue lets you browse chambers by Solo or Co-op, search by title or author, and view ratings and play counts before downloading.

No account is required to browse, download or play community chambers.

After completing a chamber, you can rate it from 1 to 5 stars. Play counts track new attempts, so continuing an existing save does not count as another playthrough.

Publishing and Accounts

To publish a chamber, sign in through your browser and connect your account to Minecraft. You can then submit your map directly from the game.

Submissions go through moderation. Your library shows whether a chamber is awaiting review, approved or rejected, along with moderator feedback. Approved chambers become available in the community catalogue.

You can update your published maps or withdraw them from the catalogue. While an update is being reviewed, the previously approved version remains available to players.

My Library

Your library keeps chamber projects, downloads and saved playthroughs organised:

• My Chambers — your projects, drafts and published or submitted maps.
• Added Chambers — maps you have downloaded or imported.
• Trash — deleted local chambers that can be restored.

Each chamber has one entry, with its versions and saved playthroughs grouped together.

You can also export and import .jtc files to share chambers directly with friends. These files include the map, starting inventory, checkpoints, gameplay settings and selected music.

Cooperative Play

Build puzzles for two players and host them using Minecraft's Open to LAN feature. Both players must reach the finish to complete a co-op chamber.

Players need the same Minecraft version and the mods required by the map. Internet co-op requires a way for the second player to reach the hosted LAN session.

Chamber Settings and Music

Open the J settings menu while building to configure Portal Gun's server settings, including portal placement rules, gravity and gel behaviour. These settings are saved with the chamber and applied to everyone playing it.

Item pickup and dropping can be controlled separately. Both are disabled by default during a run to help prevent players from losing essential equipment. Carrying cubes and other supported props remains available.

Choose from 13 background tracks, preview your selection, or use No music. Players keep their own graphics, controls and audio preferences.

Experimental Time Travel

Create puzzles across two linked eras using Justify Portal Gun's triple portal device.

The editor can generate a future copy of your chamber. Building changes made in the present carry forward into the future, while future edits stay independent. The linked rooms and timeline data travel with exported and published maps.

Time travel is an optional, experimental feature.

Justify Lasers Integration

Justify Test Chambers can also be used with Justify Lasers to build chambers around its optical devices and mechanisms.

Justify Lasers is required for maps that use its content. Install the same Justify release across all modules.

Interface and Client Settings

The mod includes a Portal 2-inspired interface, with an animated background, menu music, button sounds and transitions.

Menu music and button sounds have separate volume controls. The animated background and transitions can also be disabled in the settings.

The interface and in-game help are available in English and Russian.

Supported Versions

• Minecraft 1.20.1 — Fabric, Forge and NeoForge; Java 17.
• Minecraft 1.21.1 — Fabric, Forge and NeoForge; Java 21.
• Minecraft 26.2 — Fabric and NeoForge; Java 25.

Each Minecraft version has its own universal JAR for the loaders listed above. Choose the file for your Minecraft version. Chamber files also require a matching Minecraft version.