Help center

Help Center

Get Cairn running, learn the controls, and start capturing your builds.

Everything you need to get Cairn running, learn the controls, and start capturing your builds. Stuck on something not covered here? Reach us at hello@cairn.example.

Getting started

Cairn ships as a single cross-platform Java .jar file. To play:

Download cairn.jar from the download page.
Make sure you have Java 17 or newer installed. Not sure? Open a terminal and run java -version.
Double-click the .jar, or run java -jar cairn.jar from the folder you saved it in.

That's it — no installer, no account required to play. Your first world generates automatically.

Controls

Action	Input
Move	WASD
Jump	SPACE
Look around	Mouse
Mine (hold)	Left-click
Place block	Right-click
Select hotbar slot	1–0
Cycle hotbar	Mouse wheel
Take a photo	F2
Toggle clip recorder	F9
Cinematic camera	F8
Fly mode	F5
Menu	ESC

Mining, carrying, placing

The whole loop is mine → carry → place. Hold left-click on a block to mine it; you'll watch it crack through ten stages as it breaks. How long that takes depends on the block's hardness — soft dirt and sand come away almost instantly, while stone takes a steady hold. You can only mine what's within reach (about four and a half blocks in front of you), so step closer if nothing's happening. Mined blocks drift over and drop into your hotbar. To build, select a block with 1–0 or the mouse wheel and right-click to place it — placing is instant.

Saving & loading worlds

Worlds save locally and automatically as you play, so you rarely have to think about it. Open the menu with ESC to save on demand, return to the main menu, or load a different world. Because everything lives on your machine, you're always in control of your saves. If you'd like off-machine backups, Cairn Cabins adds server-side world backups.

The Capture Kit

Cairn has a full capture toolset built in — no extra software needed:

F2 — Screenshots. Grabs a clean, full-resolution photo of your view and saves it to your captures folder.
F9 — Clip recorder. Toggles a one-key .mp4 recorder on and off. Press once to start rolling, again to stop and save.
F8 — Cinematic camera. Engages a smooth, gliding camera for those sweeping fly-through shots of your builds.

Streaming with the OBS overlay

Cairn writes a live state.json file on your computer describing what's happening in-game. The included overlay.html reads that file and renders a ready-made overlay. To use it in OBS:

Add a new Browser source in OBS.
Point it at the local overlay.html file that ships with Cairn.
Play — the overlay updates itself from state.json as you go.

Both files stay on your machine; nothing is sent to us. There's a full streaming guide with a live preview of the overlay.

Troubleshooting

"Java not found" or the jar won't launch. Install Java 17+, then confirm with java -version. On some systems you may need to run java -jar cairn.jar from a terminal to see the error.
Black screen on startup. This is almost always graphics drivers. Update your GPU drivers to the latest version and relaunch.
No sound. Check that Cairn isn't muted in your system volume mixer, and that the right output device is selected. Ambient music can also be turned down in the game's audio settings.