Instant file previews in Windows Explorer with a single Spacebar press.
Lumos brings the beloved macOS Quick Look feature to Windows, allowing you to preview files instantly without opening them in their default applications.
- ⌨️ Spacebar Activation: Press Spacebar in Windows Explorer to instantly preview any selected file
- 🎨 Rich File Support: Preview images, PDFs, text files, audio, and video
- ⚡ Lightning Fast: <120ms latency from keypress to preview display
- 🎯 Smart Detection: Only activates in Windows Explorer, never interferes with other apps
- 🔒 Privacy First: No telemetry, no network access, completely offline
- 💾 Lightweight: Minimal memory footprint with intelligent caching
| Category | Extensions |
|---|---|
| Images | .jpg, .jpeg, .png, .gif, .bmp, .webp, .tiff, .ico |
| Documents | .pdf (requires WebView2 runtime) |
| Text | .txt, .md, .json, .xml, .log, .cs, .cpp, .h, .py, .js, .ts, .html, .css, .yaml, .yml |
| Audio | .mp3, .wav, .flac, .m4a, .wma, .aac, .ogg |
| Video | .mp4, .mkv, .avi, .mov, .wmv, .flv, .webm |
- Windows 10 (version 1809 or later) or Windows 11
- .NET 8 Runtime (Windows Desktop)
- WebView2 Runtime (for PDF previews)
- Download the latest release from the Releases page
- Install the certificate (Required for sideloading):
- Right-click the downloaded
Lumos_1.0.0.0_x64.msix - Select Properties → Digital Signatures tab
- Select the signature in the list and click Details
- Click View Certificate → Install Certificate
- Select Local Machine → Next
- Select Place all certificates in the following store
- Browse and select Trusted Root Certification Authorities → OK → Next → Finish
- If prompted for password, use "2008" and click OK
- Right-click the downloaded
- Install Lumos:
- Double-click
Lumos_1.0.0.0_x64.msix - Click "Install"
- Double-click
- Launch: Lumos starts automatically and runs in the background
- Open Windows Explorer (File Explorer)
- Navigate to any folder with files
- Select a file (single click)
- Press Spacebar to preview
- Press Spacebar, Esc, or click outside to close the preview
- Works on Desktop, in Explorer windows, and in Open/Save dialogs
- Supports rapid file browsing (just keep pressing Spacebar on different files)
- Does NOT activate when typing in search boxes or renaming files
Lumos uses a global low-level keyboard hook to detect Spacebar presses system-wide. This is essential for the Quick Look functionality.
What this means:
- Lumos monitors keyboard input to detect when you press Spacebar
- It ONLY acts when Windows Explorer is the active window
- No keystrokes are logged, recorded, or transmitted
- The hook is uninstalled when you close Lumos
Your privacy:
- ✅ No data collection
- ✅ No network access
- ✅ Completely offline
- ✅ Open source - verify the code yourself
- Visual Studio 2022 (with C++ and .NET desktop development workloads)
- Windows SDK 10.0.22621.0 or later
- .NET 8 SDK
# Clone the repository
git clone https://github.com/yourusername/Lumos.git
cd Lumos
# Restore NuGet packages
nuget restore Lumos.sln
# Build the solution
msbuild Lumos.sln /p:Configuration=Release /p:Platform=x64
# Or open Lumos.sln in Visual Studio and buildLumos/
├── core-native/ # C++ keyboard hook and Explorer integration
├── ui-managed/ # C# WPF preview window and renderers
├── shared-contracts/ # IPC data structures
├── packaging/ # MSIX packaging project
└── .github/workflows/ # CI/CD automation
- Ensure Lumos is running (check system tray)
- Verify you're in Windows Explorer (not another app)
- Try restarting Lumos
- Install WebView2 Runtime
- Restart Lumos after installing
- Ensure the certificate is installed in "Trusted Root Certification Authorities"
- Run PowerShell as Administrator and execute:
Add-AppxPackage -Path "Lumos_1.0.0.0_x64.msix"
- Lumos caches the last 5 previews in RAM
- Close and reopen Lumos to clear the cache
- Large video files may temporarily use more memory
- Open Settings → Apps → Installed apps
- Find Lumos in the list
- Click the three dots → Uninstall
- Confirm uninstallation
Lumos will be completely removed with no background services remaining.
- No telemetry: Lumos does not collect any usage data
- No network access: Completely offline, no internet connection required
- No file modifications: Read-only access to files
- No registry pollution: Minimal system footprint
- Open source: Full transparency - inspect the code yourself
MIT License - see LICENSE file for details
- Inspired by macOS Quick Look
- Built with love for the Windows community
- Special thanks to all contributors
- Issues: GitHub Issues
- Discussions: GitHub Discussions
Made with ❤️ for Windows users who miss Quick Look