---
title: Creating Your First Instance
description: Set up a modded Minecraft instance in Polymerium — pick a version and you're ready.
---

## Creating an Instance

1. Click the **+** button in the sidebar or the main area.
2. Give your instance a name (e.g. "My First Modpack").
3. Choose a **Minecraft version** — for example `1.21.4`.
4. Click **Create**.

That's it. Your instance is created — but no game files have been downloaded yet.

## What Just Happened?

In Polymerium, an instance is not a folder full of files. It's a **metadata file** (`profile.json`) that describes what your game should contain: which Minecraft version, which loader, which mods.

The actual game directory is built on demand when you **deploy** (which happens automatically when you launch for the first time). This is what makes Polymerium different from traditional launchers — and why switching loaders or adding mods later is nearly instant.

> You don't need to understand the details now. The important takeaway: **your instance is a description, not a copy**. If you're curious, read [Core Concepts → Metadata-Driven Instances](/docs/concepts/metadata-driven) later.

## Configuring Your Instance

After creating your instance, configure it before adding mods. Open the instance and switch to the **Setup** tab.

### Setting a Mod Loader

Choose a mod loader for your instance:

| Loader | Best For |
|--------|---------|
| **Fabric** | Lightweight, fast updates, large performance mod ecosystem |
| **Quilt** | Fabric-compatible with more features and faster development |
| **Forge** | The classic — biggest mod ecosystem for older versions |
| **NeoForge** | Modern Forge fork, used by many new mods for 1.20+ |

You can switch loaders at any time — that's the advantage of metadata-driven instances. Polymerium will rebuild the game directory on your next deploy.

### Memory Allocation

Override the maximum memory (JVM heap) for this instance. This is useful if a large modpack needs more RAM than your global default.

### Command Wrapper

Set a command wrapper for special cases, like `prime-run` on Linux systems with dual GPUs. The wrapper prefixes the Java launch command.

### Quick Connect

Set a server address to auto-join when the game launches. No need to type it in-game every time.

## Next Step

Your instance is configured — let's [add some mods →](/docs/getting-started/adding-mods)
