---
title: Deploy & Play
description: Deploy your instance and launch Minecraft — understand what "deploy" means and how launching works.
---

## Deploying Your Instance

Before Minecraft can run, Polymerium needs to **deploy** your instance. This is the step where your metadata (version, loader, mod list) gets turned into an actual, runnable game directory.

Click **Deploy** — or just click **Launch** and Polymerium will deploy automatically if needed.

### What Deploy Does

1. Downloads all required files — Minecraft jars, loader libraries, and mods — to the shared cache
2. Builds the game directory using **symbolic links** pointing into the cache
3. Generates launch parameters (classpath, JVM args, etc.)

### First Deploy vs. Incremental Deploys

Your first deploy downloads everything from scratch — expect it to take as long as installing a fresh modpack on any launcher. Polymerium uses an aggressive, optimized download strategy, so on a good network it can be faster than other launchers.

The real speed advantage comes on subsequent deploys. When you make small changes (add a mod, switch a loader version), Polymerium only downloads what's new or changed and rebuilds the game directory with symlinks. Incremental deploys are fast — often near-instant.

### Fast Mode

If nothing has changed since your last deploy (same mods, same versions, same settings), Polymerium **skips the deploy entirely** and goes straight to launch. This makes subsequent launches feel instant.

## Launching

Click **Launch** to start Minecraft. Polymerium supports three launch modes:

| Mode | What It Does |
|------|-------------|
| **Managed** (default) | Polymerium tracks the game process, captures output, and detects crashes. Recommended. |
| **Fire-and-forget** | Launches the game and detaches. Use this if you want to close Polymerium while playing. |
| **Debug** | Exports the full launch command for troubleshooting. Doesn't actually start the game. |

## First Launch Checklist

- [x] [Install Polymerium](/docs/getting-started/installation)
- [x] [Create an instance](/docs/getting-started/first-instance)
- [x] [Configure your instance](/docs/getting-started/first-instance#configuring-your-instance) (loader, settings)
- [x] [Add mods](/docs/getting-started/adding-mods)
- [x] Deploy and launch 🎉

## What's Next?

You're playing! Here's where to go from here:

- **Understand what just happened** — read [Core Concepts](/docs/concepts/metadata-driven) to learn why Polymerium works this way
- **Manage your instances** — [accounts](/docs/managing/accounts), [snapshots](/docs/managing/snapshots), [tags](/docs/managing/tags)
- **Go deeper** — [deployment rules](/docs/advanced/rules), [CLI](/docs/advanced/cli), [modpack development](/docs/advanced/modpack-dev)
