Native Windows Transparent Compression Tool | Free CompactGUI Alternative | Reduce Game Size | High Performance WOF Driver
CompactRS is a specialized, high-performance file compression utility built natively for the Windows NT kernel. It serves as a modern, graphical interface for the Windows Overlay Filter (WOF) API, utilizing the same transparent compression technology found in Windows "CompactOS".
Unlike traditional archivers (Zip, 7z, Rar), CompactRS performs Transparent Compression. Files processed by this utility remain fully readable and writable by the operating system, Games, and Explorer without requiring explicit decompression. This makes it a perfect CompactGUI alternative for reducing the size of:
- Steam / Epic Games installations.
- Adobe Creative Cloud apps.
- Development repositories (node_modules, target folders).
The decompression happens on-the-fly in the kernel driver level with negligible CPU overhead.
This application is engineered in pure Rust utilizing manual FFI definitions for direct Win32 API calls. It has zero external runtime dependencies (not even the windows or windows-sys crates).
- No Runtime Requirements: Does not require .NET Framework, Java, Python, or Visual C++ Redistributables.
- Ultra-Compact Binary: The output is a single, static executable file (~296 KB) that runs out-of-the-box on any Windows 10/11 system.
- Native UI: Draws standard Windows controls via
user32.dllanduxtheme.dllfor a native look and feel that respects system DPI settings.
CompactRS exposes the internal compression formats provided by Wof.sys.
| Algorithm | Compression Ratio | CPU Overhead | Ideal Use Case |
|---|---|---|---|
| XPRESS4K | Low | Very Low | Frequently accessed system files, logs. |
| XPRESS8K | Medium | Low | General documents, non-media assets. |
| XPRESS16K | High | Medium | Applications, larger binaries. |
| LZX | Very High | High | Games, archival data, static software (Read-heavy). |
Pro Tip: LZX is the gold standard for game compression, capable of reducing installation sizes by 30-60% with zero impact on loading times for most titles.
Built directly on top of the Windows Message Loop (GetMessage, DispatchMessage). It uses a Facade pattern to wrap raw CreateWindowExW calls into safe Rust components, ensuring high performance and low memory footprint (~4MB RAM usage).
- Multithreading: Implements a work-stealing thread pool to saturate modern multi-core CPUs during the analysis and compression phases.
- Safety Heuristics: Automatically detects and skips incompressible file types (e.g.,
.mp4,.zip,.jpg) to prevent wasted CPU cycles. - Lock Handling: Integrates with the Windows Restart Manager API. If a file is locked by another process (e.g., a running game), CompactRS identifies the blocker and offers a prompt to terminate it cleanly before proceeding.
- Per-Monitor V2 DPI Awareness: Crisp text and UI rendering on 4K monitors and mixed-scale setups.
- Immersive Dark Mode: Uses undocumented Windows APIs (Ordinal 133/135 in
uxtheme.dll) to apply system-consistent dark theming to legacy Win32 controls, menus, and window frames.
| Feature | CompactRS | Compactor | CompactGUI | compact.exe |
|---|---|---|---|---|
| Interface | Native Win32 UI | WebView UI | Modern WPF GUI | CLI |
| Language | Rust (Manual FFI) | Rust | C# / .NET 9 | C/C++ |
| Binary Size | ~296 KB | ~617 KB (.zip) | ~10 MB (+Runtime) ~67 MB (Standalone) |
N/A (Built-in) |
| Dependencies | Zero (Static) | WebView2 | .NET 9 Desktop Runtime | None |
| Memory | ~3-4 MB | ~20 MB+ | ~60 MB+ | Low |
| Compresstimation | Yes (Heuristic) | Yes (Statistical) | No | No |
| Folder Monitoring | Yes | No | Yes | No |
| Game Database | No | No | Yes | No |
| Pause/Resume | Yes | Yes | Yes | No |
- OS: Windows 10 (Build 17763+) or Windows 11.
- Privileges: Administrator rights are strictly required. The WOF driver (
fsctl) operations are privileged kernel commands.
- Navigate to the Releases Page.
- Download
compactrs.exe. - Right-click the file and select Run as Administrator.
- Add Target: Drag and drop folders or files onto the application window, or use the Files / Folder buttons in the bottom action bar.
- Configuration:
- Action Mode: Select "Compress All" or "Decompress All".
- Algorithm: Select desired strength (Default:
XPRESS8K).- Tip: Use LZX for game folders to save maximum space.
- Force: Check this to force compression on files that the OS deems "not beneficial" or locked files (triggers Lock Handler).
- Execute: Click Process All.
- Monitor: The list view updates in real-time, showing:
- Logical Size: The actual size of the data.
- Physical Size: The size on disk after compression.
- Status: Success, Skipped, or Error details.
If a file is in use, a dialog will appear showing the Process Name and PID holding the lock.
- Force Stop: Terminates the blocking process and retries compression immediately.
- Cancel: Skips the current file.
A: Yes. CompactRS uses the official Windows Overlay Filter (WOF) API, which is the same technology Windows uses for "CompactOS". It is natively supported by the kernel.
A: Generally, no. Modern CPUs (even older ones) can decompress XPRESS/LZX data faster than the disk can read it. In many cases, loading times improve because less data is being read from the disk.
A: CompactRS offers similar functionality to CompactGUI but is written in Rust, has zero dependencies (no .NET required), and is significantly lighter/faster to start.
A: No. The WOF API was introduced in Windows 10.
To compile CompactRS, you must have the Rust Toolchain (MSVC ABI) installed.
# 1. Clone the repository
git clone https://github.com/IRedDragonICY/compactrs.git
cd compactrs
# 2. Build for Release
# The profile is configured for maximum size optimization (lto, strip, opt-level="z")
cargo build --release
