Creating Your First Instance

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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 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:

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 →