GitHub - Mateuscruz19/Ext4Windows: A lightweight ext4 filesystem driver for Windows built with C++, WinFsp, and lwext4. Mount your Linux partitions as native Windows drive letters.

Mount Linux ext4 partitions as native Windows drive letters.
_{No VM. No WSL. No hassle. Just plug and browse.}

_{🌍 **English** · Português · Español · Deutsch · Français · 中文 · 日本語 · Русский}

Quick Start Installation Build from Source Report Bug

The Problem

Dual-booting Linux and Windows is common. Accessing your Linux files from Windows? Painful.

Windows has zero native ext4 support. Your Linux partition is invisible. Your files are trapped behind a filesystem Windows refuses to read.

The existing solutions all have serious drawbacks:

Tool	Problem
Ext2Fsd	Abandoned since 2017. Kernel-mode driver = BSOD risk. No ext4 extent support.
Paragon ExtFS	Paid software ($40+). Closed source.
DiskInternals Reader	Read-only. No drive letter — files are accessed through a clunky custom UI.
WSL `wsl --mount`	Runs inside a Hyper-V VM. Requires admin. Not a real drive letter. Files accessed through `\\wsl$\` path.

The Solution

Ext4Windows mounts ext4 filesystems as real Windows drive letters. Your Linux files show up in Explorer, just like any USB drive. Open, edit, copy, delete — everything works natively.

C:\> ext4windows mount D:\linux.img
  OK Mounted D:\linux.img on Z: (read-only)

Your ext4 files are now on Z: — browse them in Explorer, open them in any app, drag & drop. Done.

Features

Core Mount ext4 images (`.img`) as drive letters Mount raw ext4 partitions from physical disks Full read support — files, directories, symlinks Full write support — create, edit, delete, copy, rename Multiple simultaneous mounts (Z:, Y:, X:, ...)	Architecture Background server with system tray icon CLI client for scripting and automation Named Pipe IPC for fast client-server communication Auto-start server on first mount command Graceful cleanup on eject/unmount
Usability Auto-detect ext4 partitions with `scan` Auto-select free drive letter (Z: down to D:) Right-click tray icon to unmount or quit Legacy one-shot mode for simple usage Debug logging for troubleshooting	Technical Userspace driver — no kernel module, no BSOD risk Per-instance ext4 device names (multi-mount safe) Global mutex for lwext4 thread safety Open-per-operation pattern (no handle leaks) Ghost mount detection and auto-cleanup

Comparison

How does Ext4Windows stack up against the alternatives?

Feature	Ext4Windows	Ext2Fsd	DiskInternals	Paragon	WSL `--mount`
Real drive letter	✅	✅	❌	✅	❌
Read support	✅	✅	✅	✅	✅
Write support	✅	⚠️ Partial	❌	✅	✅
ext4 extents	✅	❌	✅	✅	✅
No reboot needed	✅	❌	✅	✅	✅
No admin required	✅	❌	✅	❌	❌
System tray GUI	✅	❌	✅	✅	❌
Open source	✅	✅	❌	❌	❌
Actively maintained	✅	❌ (2017)	❌	✅	✅
Userspace (no BSOD)	✅	❌	✅	❌	✅
Free	✅	✅	✅	❌ ($40+)	✅

Quick Start

Mount an ext4 image

# Mount read-only (default) — auto-selects drive letter
ext4windows mount path\to\image.img

# Mount on a specific drive letter
ext4windows mount path\to\image.img X:

# Mount with write support
ext4windows mount path\to\image.img --rw

# Mount with write support on specific letter
ext4windows mount path\to\image.img X: --rw

Manage mounts

# Check what's mounted
ext4windows status

# Unmount a drive
ext4windows unmount Z:

# Scan for ext4 partitions on physical disks (requires admin)
ext4windows scan

# Shut down the background server
ext4windows quit

Legacy mode

For quick one-off usage without the client-server architecture:

# Mount and block until Ctrl+C
ext4windows path\to\image.img Z:

# Mount read-write in legacy mode
ext4windows path\to\image.img Z: --rw

Architecture

Ext4Windows uses a client-server architecture. The first mount command auto-starts a background server, which manages all mounts and shows a system tray icon.

graph TB
    subgraph Client ["CLI Client"]
        A["ext4windows mount ..."]
        B["ext4windows status"]
        C["ext4windows unmount Z:"]
    end

    subgraph Pipe ["Named Pipe IPC"]
        D["\\.\pipe\ext4windows"]
    end

    subgraph Server ["Background Server"]
        E["MountManager"]
        F["Mount Z: → Ext4FS"]
        G["Mount Y: → Ext4FS"]
        H["System Tray Icon"]
    end

    subgraph Stack ["Filesystem Stack"]
        I["WinFsp (FUSE)"]
        J["lwext4 Library"]
        K["ext4 Partition / Image"]
    end

    A --> D
    B --> D
    C --> D
    D --> E
    E --> F
    E --> G
    E --> H
    F --> I
    G --> I
    I --> J
    J --> K

    style A fill:#1B1464,color:#fff,stroke:#1B1464
    style B fill:#1B1464,color:#fff,stroke:#1B1464
    style C fill:#1B1464,color:#fff,stroke:#1B1464
    style D fill:#F5841F,color:#fff,stroke:#F5841F
    style E fill:#F5841F,color:#fff,stroke:#F5841F
    style H fill:#F5841F,color:#fff,stroke:#F5841F
    style F fill:#1B1464,color:#fff,stroke:#1B1464
    style G fill:#1B1464,color:#fff,stroke:#1B1464
    style I fill:#1B1464,color:#fff,stroke:#1B1464
    style J fill:#1B1464,color:#fff,stroke:#1B1464
    style K fill:#F5841F,color:#fff,stroke:#F5841F

How a file read works

When you open a file in Explorer on the mounted drive, here's what happens under the hood:

Explorer opens Z:\docs\readme.txt
  → Windows kernel sends IRP_MJ_READ to WinFsp driver
    → WinFsp calls our OnRead callback in Ext4FileSystem
      → We lock the global ext4 mutex
        → lwext4 opens the file: ext4_fopen("/mnt_Z/docs/readme.txt", "rb")
        → lwext4 reads the requested bytes: ext4_fread()
        → lwext4 closes the file: ext4_fclose()
      → We unlock the mutex
    → Data flows back through WinFsp to the kernel
  → Explorer displays the file content

System Tray

The server creates a system tray icon (notification area) using pure Win32 API:

Hover the icon to see mount count
Right-click to see active mounts, unmount drives, or quit
The icon uses the Ext4Windows logo (embedded in the exe via resource file)
If a drive is ejected via Explorer, the server detects it and auto-cleans the ghost mount

Installation

Prerequisites

Windows 10 or 11 (64-bit)

Download

Download	Description
Ext4Windows-setup.exe	Installer — installs everything automatically (recommended)
Ext4Windows-portable.zip	Portable — extract and run (requires WinFsp installed)

Verify it works

# Create a test ext4 image using WSL (if available)
wsl -e bash -c "dd if=/dev/zero of=/tmp/test.img bs=1M count=64 && mkfs.ext4 /tmp/test.img"
cp \\wsl$\Ubuntu\tmp\test.img .

# Mount it
ext4windows mount test.img

Building from Source

Prerequisites

Tool	Version	Purpose
Windows	10 or 11	Target OS
Visual Studio 2022	Build Tools or full IDE	C++ compiler (MSVC)
CMake	3.16+	Build system
Git	Any	Clone with submodules
WinFsp	Latest	FUSE framework + SDK

Note: You need the "Desktop development with C++" workload in Visual Studio.

Clone

git clone --recursive https://github.com/Mateuscruz19/Ext4Windows.git
cd Ext4Windows

The --recursive flag is important — it pulls the lwext4 submodule from external/lwext4/.

Build

Open a Developer Command Prompt for VS 2022 (or run VsDevCmd.bat), then:

mkdir build
cd build
cmake ..
cmake --build .

The executable will be at build\ext4windows.exe.

Quick build script

If you have VS Build Tools installed, just run:

build.bat

This script automatically sets up the VS environment and builds.

Project structure

Ext4Windows/
├── .github/workflows/         # CI/CD (build, test, release)
├── assets/                    # Logo, icons, screenshots
├── cmake/                     # CMake modules (FindWinFsp)
├── docs/                      # Translated READMEs (7 languages)
├── external/
│   ├── lwext4/                # lwext4 submodule (ext4 implementation)
│   └── catch2/                # Catch2 test framework (amalgamated)
├── installer/
│   └── ext4windows.iss        # Inno Setup script (auto-installs WinFsp)
├── src/
│   ├── main.cpp               # Entry point and argument routing
│   ├── ext4_filesystem.cpp/hpp  # WinFsp filesystem callbacks
│   ├── server.cpp/hpp         # Background server + MountManager
│   ├── client.cpp/hpp         # CLI client
│   ├── tray_icon.cpp/hpp      # System tray icon (Win32)
│   ├── interactive.cpp/hpp    # Interactive terminal mode (8 languages)
│   ├── pipe_protocol.hpp      # Named Pipe IPC protocol
│   ├── blockdev_file.cpp/hpp  # Block device from .img file
│   ├── blockdev_partition.cpp/hpp  # Block device from raw partition
│   ├── partition_scanner.cpp/hpp   # Ext4 partition auto-detection
│   ├── debug_log.hpp          # Debug logging utilities
│   └── ext4windows.rc         # Windows resource file (icon)
├── tests/                     # 110 tests (Catch2)
├── CMakeLists.txt             # Build configuration
├── CHANGELOG.md               # Version history
├── CONTRIBUTING.md            # Contribution guidelines
└── LICENSE                    # GPL-2.0

Tech Stack

_{Core language}

_{Virtual filesystem}

_{ext4 implementation}

_{Tray, pipes, processes}

_{Build system}

Library	Role	Link
WinFsp	Windows FUSE framework. Creates virtual filesystems that appear as real drives. Handles all kernel communication — we just implement callbacks (OnRead, OnWrite, OnCreate, etc.)	winfsp.dev
lwext4	Portable ext4 filesystem library in pure C. Reads and writes the ext4 on-disk format: superblock, block groups, inodes, extents, directory entries. We use it as a submodule.	github.com/gkostka/lwext4
Win32 API	Native Windows APIs for system tray icon (`Shell_NotifyIconW`), named pipes (`CreateNamedPipeW`), process management (`CreateProcessW`), and drive letter detection (`GetLogicalDrives`).	learn.microsoft.com

Security & Memory Safety

Ext4Windows is audited with four independent analysis tools. All tests are run on every release.

Tool	What it checks	Result
AddressSanitizer (ASan) _{/fsanitize=address}	Buffer overflows, use-after-free, stack corruption, heap corruption — detected at runtime during a full mount → read → write → unmount → quit cycle	PASS — 0 errors
MSVC Code Analysis _/analyze	Static analysis for null pointer dereferences, buffer overruns, uninitialized memory, integer overflows, security anti-patterns (C6000–C28000 rules)	PASS — 0 vulnerabilities _{7 informational warnings (handle null checks — all guarded at runtime)}
CppCheck 2.20 _{--enable=all --inconclusive}	Independent static analyzer (183 checkers): buffer overflows, null dereferences, resource leaks, uninitialized variables, portability issues	PASS — 0 bugs, 0 vulnerabilities _{Style-only suggestions (const correctness, unused variables)}
CRT Debug Heap _{_CrtDumpMemoryLeaks}	Memory leaks — tracks every `new`/`malloc` and reports anything not freed at exit. Tested: blockdev create/destroy, full ext4 mount/read/unmount cycle	PASS — 0 leaks

Security hardening measures

Protection	Description
Named Pipe ACL	Pipe restricted to creator user via SDDL `D:(A;;GA;;;CU)` — other users on the system cannot send commands
Path traversal prevention	All paths validated against `..` sequences and null bytes before processing
Drive letter validation	Only `A-Z` accepted as drive letters in MOUNT/MOUNT_PARTITION commands
Integer overflow guards	Block read/write sizes checked before multiplication to prevent DWORD overflow
Explicit process path	`CreateProcessW` uses explicit exe path (no PATH search hijacking)
Bounded string copies	All `wcscpy` replaced with `wcsncpy` + null terminator to prevent buffer overflow
Userspace driver	No kernel module — a crash cannot cause BSOD or corrupt system memory

Test Suite

Ext4Windows uses Catch2 for automated testing. The suite covers validation, security, string handling, timestamps, permissions, and ext4 integration.

test_validation   — 153 assertions in 21 tests   (drive letters, path traversal, overflow guards)
test_string_utils —  34 assertions in 16 tests   (UTF-8 conversion, path mapping, roundtrips)
test_timestamps   — 1018 assertions in 11 tests  (POSIX ↔ FILETIME, epoch, Y2K38, roundtrips)
test_permissions  —  67 assertions in 23 tests   (mode bits, hidden files, READONLY, NORMAL)
test_format_size  —  24 assertions in 24 tests   (bytes, MB, GB, TB, GUID comparison)
test_blockdev     —  63 assertions in 15 tests   (create/destroy, mount/read/unmount, timestamps)
─────────────────────────────────────────────────
TOTAL               1359 assertions in 110 tests  ✅ ALL PASSED

Running the tests

cd build
cmake ..
cmake --build .
cd tests
ctest --output-on-failure

Roadmap

v1.0.0 — Complete

v1.1.0 — Complete

WebView2 GUI (dark theme, sidebar navigation)
Mount, Scan, Status, Settings, About pages
Server health monitoring with auto-restart
Custom drive icon in Windows Explorer (HKLM registry)
New logo (disk + Tux + Windows)

Future Ideas

ext4 encryption support
Drag-and-drop .img files onto the exe to mount

FAQ

Is this safe? Can it corrupt my Linux partition?

Ext4Windows runs entirely in userspace (thanks to WinFsp), so it cannot cause a Blue Screen of Death (BSOD). The codebase is audited with AddressSanitizer, MSVC static analysis, and CRT leak detection — see Security & Memory Safety. For safety, the default mount mode is read-only. Write mode (--rw) includes ext4 journaling support for crash recovery. Always keep backups.

Do I need admin privileges?

No — for mounting image files (.img), no admin is needed. The scan command (which scans physical disks) does require admin because it needs to access raw disk devices (\\.\PhysicalDrive0, etc.). The program will automatically prompt for UAC elevation when needed.

What ext4 features are supported?

lwext4 supports the core ext4 features: extents, 64-bit block addressing, directory indexing (htree), metadata checksums, and journaling (recovery + write transactions). Features not supported: inline data, encryption, and verity.

Can I mount ext2 or ext3 partitions?

Yes! ext4 is backwards-compatible with ext2 and ext3. lwext4 can read all three formats.

Does it work with dual-boot Linux partitions?

Yes, that's the primary use case. Use ext4windows scan to find and mount your Linux partition. Important: do not mount your Linux root partition with --rw while Linux might be using it (e.g., if you're running WSL). This can cause data corruption.

Why not just use WSL `wsl --mount`?

WSL mounts partitions inside a Hyper-V virtual machine. The files are accessible only through \\wsl$\ network path, not as a real drive letter. It requires admin, has higher overhead, and doesn't integrate with Windows Explorer the same way a real drive does.

Can I use this with USB drives formatted as ext4?

Yes! Use ext4windows scan to detect the ext4 partition on the USB drive, then mount it.

The tray icon disappeared. What happened?

The server might have crashed or been killed. Run ext4windows status — if the server isn't running, the next mount command will auto-start it.

How do I enable debug logging?

Add --debug to any command:

ext4windows mount image.img --debug

For the server, debug logs are written to %TEMP%\ext4windows_server.log.

Troubleshooting

"Error: could not start server"

The server process failed to launch. Possible causes:

Another instance is already running — try ext4windows quit first
Antivirus is blocking the process — add an exception for ext4windows.exe
WinFsp is not installed — download from winfsp.dev/rel

"Error: server did not start in time"

The server started but the named pipe wasn't created within 3 seconds. This can happen if:

WinFsp DLL (winfsp-x64.dll) is not found — make sure it's in the same directory as ext4windows.exe or WinFsp is installed system-wide
The system is under heavy load — try again

"Mount failed (status=0xC00000XX)"

WinFsp returned an error during mount. Common codes:

0xC0000034 — Drive letter already in use by another program
0xC0000022 — Permission denied (try running as admin)
0xC000000F — File not found (check the image path)

"Error: server is busy, try again"

The server handles one command at a time. If another client is currently communicating, you'll get this error. Just retry.

Files show 0 bytes or can't be opened

This usually means the ext4 image is corrupted or uses unsupported features. Try:

Check the image with fsck.ext4 in Linux/WSL
Enable debug logging (--debug) to see the specific error
Try mounting read-only first (remove --rw)

Drive disappeared from Explorer

If you eject the drive from Explorer (right-click → Eject), the server detects this and cleans up automatically. Run ext4windows status to confirm. To re-mount, run the mount command again.

Contributing

Contributions are welcome! This project is actively developed and there's plenty to do.

Fork the repository
Create a feature branch (git checkout -b feature/amazing-thing)
Commit your changes
Push to the branch
Open a Pull Request

Check the Roadmap for ideas on what to work on. Feel free to open an issue for discussion before starting large changes.

License

This project is licensed under the GNU General Public License v2.0 — see the LICENSE file for details.

_{Built with WinFsp and lwext4. Logo inspired by the Linux penguin footprint and Windows window.}

Name		Name	Last commit message	Last commit date
Latest commit History 81 Commits
.github/workflows		.github/workflows
assets		assets
cmake		cmake
docs		docs
external		external
installer		installer
src		src
tests		tests
.gitignore		.gitignore
.gitmodules		.gitmodules
CHANGELOG.md		CHANGELOG.md
CLAUDE.md		CLAUDE.md
CMakeLists.txt		CMakeLists.txt
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md

Folders and files

Latest commit

History

Repository files navigation

The Problem

The Solution

Features

Core

Architecture

Usability

Technical

Comparison

Quick Start

Mount an ext4 image

Manage mounts

Legacy mode

Architecture

How a file read works

System Tray

Installation

Prerequisites

Download

Verify it works

Building from Source

Prerequisites

Clone

Build

Quick build script

Project structure

Tech Stack

Security & Memory Safety

Security hardening measures

Test Suite

Running the tests

Roadmap

v1.0.0 — Complete

v1.1.0 — Complete

Future Ideas

FAQ

Is this safe? Can it corrupt my Linux partition?

Do I need admin privileges?

What ext4 features are supported?

Can I mount ext2 or ext3 partitions?

Does it work with dual-boot Linux partitions?

Why not just use WSL wsl --mount?

Can I use this with USB drives formatted as ext4?

The tray icon disappeared. What happened?

How do I enable debug logging?

Troubleshooting

"Error: could not start server"

"Error: server did not start in time"

"Mount failed (status=0xC00000XX)"

"Error: server is busy, try again"

Files show 0 bytes or can't be opened

Drive disappeared from Explorer

Contributing

License

About

Resources

Contributing

Stars

Watchers

Forks

Releases

Packages

Contributors

Languages

Why not just use WSL `wsl --mount`?