Polymerium

<a href="https://polymerium.dearain.dev"> <picture> <source media="(prefers-color-scheme: dark)" srcset="assets/brand/banner-dark.svg"> <source media="(prefers-color-scheme: light)" srcset="assets/brand/banner-light.svg"> <img alt="Polymerium" src="assets/brand/banner-light.svg"> </picture> </a> <div align="center">

A Minecraft instance manager built on a simple idea.

🌐 中文介绍 • 📥 Download • 📖 Documentation • 🐛 Report Bug • 💡 Request Feature

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In action

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From opening the app to launching the game.

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What makes it different

An instance in Polymerium is a description, not a pile of copied files.

Change the loader, swap mods in and out, update the whole pack — the description changes, Polymerium rebuilds the files on demand, and your saves and settings stay put.

• Switch loaders without rebuilding. Forge to NeoForge, Fabric to Quilt — change the loader, redeploy, keep your mods.
• Update modpacks in place. Drop in a new version; your saves, settings and worlds carry over.
• Roll back anything. Every change can be snapshotted. Break something? One click restores it, with a diff of exactly what moved.

Because files are linked instead of duplicated, ten modpacks sharing the same mods don't cost ten times the disk. Your whole setup fits in a tiny config file — version-control it, share it, move it between machines.

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Features

<div align="center"> <table> <tr> <td width="55%" valign="top"> <b>Everything at a glance</b><br><br> All your instances, accounts, and the worlds you've been playing — in one place. Jump back into what you were doing, or start something new. </td> <td width="45%"> <img src="assets/screenshots/landing.png" alt="Home dashboard"> </td> </tr> <tr> <td width="45%"> <img src="assets/screenshots/instance.png" alt="Instance home with launch pad"> </td> <td width="55%" valign="top"> <b>Deploy and launch</b><br><br> Pick an instance, hit play. Polymerium turns the metadata into a running game in one step — no manual file juggling, and jumping to another instance is instant. </td> </tr> <tr> <td width="55%" valign="top"> <b>Manage mods, not files</b><br><br> Browse, filter, enable and update mods as entries in a list — not as files in a folder. Switch between list and grid, filter by source or type, update one mod or the whole pack. </td> <td width="45%"> <img src="assets/screenshots/setup.png" alt="Mod management"> </td> </tr> <tr> <td width="45%"> <img src="assets/screenshots/graph.png" alt="Dependency graph"> </td> <td width="55%" valign="top"> <b>See the full dependency graph</b><br><br> Every mod and every layer of dependency, laid out visually. Spot conflicts and missing requirements before you ever hit launch. </td> </tr> <tr> <td width="55%" valign="top"> <b>Install from the big marketplaces</b><br><br> CurseForge and Modrinth, built in. Search, filter by game version and loader, and install straight into an instance without leaving the app. </td> <td width="45%"> <img src="assets/screenshots/marketplace.png" alt="Marketplace search"> </td> </tr> </table> </div>

And more

• Snapshots — save and restore complete game states, with a diff view of what changed.
• Git-friendly modpacks — an instance is a config file, so you can version-control your pack and collaborate on it.
• Cross-platform — Windows, Linux and macOS (Apple Silicon) from one codebase.
• Clean uninstall — remove Polymerium entirely by deleting two folders.

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Getting Started

Installation

[!NOTE] Polymerium is in active development. Features and UI may change between releases.

Microsoft OAuth · Open source MIT · Credentials never leave your machine.

Before downloading, check the note for your platform:

<details> <summary>🪟 <strong>Windows</strong> — enable Developer Mode (required for symlinks)</summary>

Polymerium uses symbolic links for efficient file management. Enable Developer Mode to allow symlink creation without administrator privileges.

Windows 11

Settings → System → For developers → Developer Mode

Windows 10

Settings → Update & Security → For developers → Developer Mode

Windows 7/8

Upgrade to Windows 10+ first 💥

</details> <details> <summary>🍎 <strong>macOS</strong> — "Installer is damaged" workaround</summary>

The PKG installer is not signed with an Apple Developer certificate, so macOS Gatekeeper may block it with a "damaged" message.

1. Right-click the .pkg file and choose Open.

2. If that doesn't work, remove the quarantine flag from Terminal:

   xattr -d com.apple.quarantine Polymerium-osx-arm64-Setup.pkg
   

3. Open the .pkg file again and follow the installer.

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| Platform | Package | Direct Download | |---------------------|---------------|-----------------------------------------------------------------------------------------------------| | Windows x64 | Installer | Download | | Linux x64 | AppImage | Download | | macOS Apple Silicon | PKG installer | Download |

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1. Download the package for your platform
2. Run the installer or executable
3. Follow the setup wizard to configure your first instance

Quick start

1. Create an instance — pick a Minecraft version and a mod loader
2. Add content — install mods from CurseForge or Modrinth
3. Deploy — Polymerium builds the game files
4. Play — launch it, or export the whole thing as a modpack

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Architecture

| Technology | Purpose | Integration | |--------------------------|----------------------------------|----------------------| | .NET 10 | Runtime with C# preview features | Core platform | | Avalonia 12 | Cross-platform XAML UI framework | Presentation | | MVVM | Separation of concerns | Architecture pattern | | Dependency Injection | Modular, testable services | Service management | | Reactive Extensions | Responsive data flow | Data flow |

Project structure

Polymerium/
├── website/        # Documentation & project site
├── src/            # Application source code
├── submodules/     # Embedded third-party project sources
├── notes/          # Internal notes
├── changelogs/     # Version changelogs
├── scripts/        # Build & publish scripts
├── assets/         # Screensho