https://github.com/steamclienthomebrew/millennium
An open-source low-code modding framework to create, manage and use themes/plugins for the desktop Steam Client without any low-level internal interaction or overhead.
https://github.com/steamclienthomebrew/millennium
millennium patcher plugins-api reverse-engineering skins steam themes valve
Last synced: 26 days ago
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An open-source low-code modding framework to create, manage and use themes/plugins for the desktop Steam Client without any low-level internal interaction or overhead.
- Host: GitHub
- URL: https://github.com/steamclienthomebrew/millennium
- Owner: SteamClientHomebrew
- License: mit
- Created: 2023-04-30T18:06:18.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2026-03-31T17:44:38.000Z (3 months ago)
- Last Synced: 2026-04-03T01:12:23.280Z (3 months ago)
- Topics: millennium, patcher, plugins-api, reverse-engineering, skins, steam, themes, valve
- Language: C++
- Homepage: https://steambrew.app
- Size: 103 MB
- Stars: 3,254
- Watchers: 24
- Forks: 117
- Open Issues: 22
-
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yml
- License: LICENSE.md
Awesome Lists containing this project
README
Millennium is an **open-source low-code modding framework** to create, manage and use themes/plugins
for the desktop Steam Client without any low-level internal interaction or overhead.
If you enjoy this tool, please consider starring the project ⭐
## Installation
Installing Millennium is only a few steps. See [this page](https://docs.steambrew.app/users/installing) for a more detailed guide.
## Features
### Plugins
- **TypeScript ([React](https://react.dev/)) frontend** container in Steam
- **Lua backend** container in [usermode](https://en.wikipedia.org/wiki/User-Mode_Driver_Framework)
- **[Foreign function interface](https://en.wikipedia.org/wiki/Foreign_function_interface)** binding from **Lua** to **TypeScript** and vice versa
- **Hook modules in the Steam web browser**
- Overwrite/Modify HTTP requests
- Load custom JavaScript (Native) into web browser
- Load custom StyleSheets into web browser
### Themes
- Manage and load custom themes written in JavaScript and CSS.
- Inject JavaScript modules and CSS modules into specific Steam windows,
- Provide customizable color, style, and javascript options for your theme,
letting users personalize their experience without touching any code
## Official Plugin Repository
Millennium is designed to be fully extensible through plugins.
To ensure version compatibility and safety, we maintain a separate, curated [PluginDatabase](https://github.com/SteamClientHomebrew/PluginDatabase) repository.
All plugins in the PluginDatabase are versioned and reviewed to work seamlessly with the current Millennium release, reducing the risk of conflicts or instability when adding new features.
**For more related information, checkout the [plugin database](https://github.com/SteamClientHomebrew/PluginDatabase)**.
## Adding Languages
Only languages officially supported by the Steam can be added to the Millennium. Check the list [here](https://partner.steamgames.com/doc/store/localization/languages) in the `Full Platform Supported Languages` section.
To add your spoken language to Millennium, fork this repository and place your language json (based on the [english locale](./src/locales/english.json)) among the [current locales](./src/locales). Name the file `{your_language}.json` where `your_language` is the `API language code` from the [supported language list](https://partner.steamgames.com/doc/store/localization/languages) and append the target file to the `localizationFiles` in [this file](./src/typescript/frontend/utils/localization-manager.ts).
Millennium is only maintaining the english language, and if any changes are made to the english locales that don't reflect on a target language, contributors are responsible for updating them.
## Creating Plugins & Themes
Creating themes and plugins for Millennium is relatively straight foward. Our [documentation](https://docs.steambrew.app/developers) goes over the basics of both,
and we have examples for both [plugins](https://github.com/SteamClientHomebrew/PluginTemplate) and [themes](https://github.com/SteamClientHomebrew/ThemeTemplate)
## Platform Support
Supported Platforms:
- Windows (x86/x64/ARM) NT (10 and newer)
- Linux (x86/x86_64/i686/i386)
- macOS (experimental wrapper app install via `./scripts/install_macos.sh`, legacy tier0 via `--tier0-legacy`, development launch via `./scripts/launch_macos.sh`)
## Building from Source
### Linux
#### Prerequisites
**Arch Linux** (other distros need equivalent packages):
```
cmake ninja bun
lib32-gcc-libs lib32-openssl lib32-libidn2 lib32-xz lib32-zstd lib32-brotli lib32-libnghttp2 lib32-libpsl
libx11 libxtst
```
#### Build
```bash
cmake --preset linux-debug
cmake --build build
```
For a release build, use `linux-release` instead.
#### Dev Environment Setup
After building, run the setup script to symlink the build outputs into Steam's runtime directories:
```bash
./scripts/linux/setup_devenv.sh
```
This only needs to be run **once** — the symlinks point into the build tree, so rebuilding automatically picks up changes without re-running the script. Just restart Steam after rebuilding.
To remove the symlinks and restore Steam to its stock state:
```bash
./scripts/linux/destroy_devenv.sh
```
### Windows
#### Prerequisites
- [Visual Studio Build Tools](https://aka.ms/vs/17/release/vs_buildtools.exe) (with the "Desktop development with C++" workload — includes CMake and Ninja, add them to PATH)
- [Bun](https://bun.sh/)
#### Build
Open a **Developer PowerShell for VS**, then:
```powershell
cmake --preset windows-debug
cmake --build build
```
For a release build, use `windows-release` instead.
On Windows, CMake automatically detects your Steam installation from the registry and outputs binaries directly into Steam's directory. No additional setup is needed — just restart Steam after building.
## Sponsors
| 
| Free code signing on Windows provided by [SignPath.io](https://signpath.io/), certificate by [SignPath Foundation](https://signpath.org/) |
| :--- | :--- |