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FileFlash

Fast LAN file sharing with offline-capable PWA and real-time sync

Python 3.13+ FastAPI Docker License: MIT

🚀 Overview

FileFlash is a lightweight, high-performance file-sharing application optimized for local area networks (LANs). It provides a modern, responsive web interface for managing shared files with a focus on simplicity, speed, and offline capability.

Perfect for home networks, office LANs, workgroups, and edge computing scenarios where you need quick, authenticated-free file sharing on the same network.

✨ Features

Core File Operations

  • Upload Files with real-time progress tracking and drag-and-drop support
  • Download Files with automatic content-type detection
  • Rename Files with inline editing
  • Delete Files with safety confirmation
  • List Files sorted by modification date (newest first)
  • File Metadata including size and last modified timestamp

User Interface

  • Responsive Design - Works seamlessly on desktop, tablet, and mobile
  • Dual View Modes - Table view on desktop, card view on mobile
  • Real-time Upload Progress - Visual feedback with percentage and file name
  • Empty State - Clean, intuitive UI when no files exist
  • Toast Notifications - Non-intrusive status messages
  • Dark/Light Mode Support - Via system preferences
  • Icons & Branding - Professional FileFlash logo and styling

Progressive Web App (PWA)

  • Offline Support - App shell caches core assets for offline browsing
  • Web App Manifest - Installable as standalone app on phones/tablets
  • Service Worker - Smart caching strategy with network-first data fetching
  • Background Sync Queue - Queue operations (upload, rename, delete) when offline
  • Automatic Sync - Polls every 15 seconds to sync queued operations when reconnected
  • Offline Indicators - Clear visual badges showing online/offline status and pending sync items

Media Viewing

  • Image Gallery - View JPG, PNG, GIF, WebP, AVIF, SVG with PhotoSwipe lightbox
  • Video Player - Stream MP4, WebM, MOV, OGV with Plyr player
  • Audio Player - Play MP3, WAV, OGG, M4A, FLAC with Plyr player
  • PDF Viewer - View PDF files with page navigation (previous/next)
  • Inline Previews - View media without downloading (uses content-disposition: inline)

Performance & Storage

  • Minimal Dependencies - Only FastAPI, uvicorn, and python-multipart
  • Chunked Uploads - Configurable chunk size (default: 1MB) for reliable large file handling
  • Atomic File Operations - Temporary files prevent partial uploads on errors
  • Efficient List Operations - Direct filesystem scanning with minimal overhead
  • Lightweight Frontend - Vanilla JavaScript, no frameworks (bundles Tailwind CSS and CDN resources)

Security & Validation

  • Filename Validation - Prevents directory traversal and null bytes
  • Upload Size Limits - Configurable max file size (default: 512MB)
  • Conflict Detection - Prevents overwriting files during upload or rename
  • Temporary File Cleanup - Removes incomplete uploads on error
  • Content-Type Detection - Automatic MIME type detection for downloads

Configuration & Deployment

  • Environment Configuration - All settings via environment variables
  • Docker Support - Multi-stage Dockerfile with uv for fast builds
  • Docker Compose - Ready-to-use production setup with persistent volumes
  • Health Check - /healthz endpoint for monitoring
  • Optional API Docs - Swagger docs (disabled by default for security)
  • Configurable Paths - Point to any filesystem location for shared files

📋 Requirements

  • Python 3.13+ (for local mode)
  • uv - Fast, modern Python package manager

Minimal Footprint

  • No database required
  • No external authentication service
  • Works standalone or behind reverse proxy

🚀 Quick Start

Choose one of three ways to run FileFlash:

Mode 1: Locally with Python + uv

Perfect for development and testing.

Mac/Linux:

# Clone the repository
git clone https://github.com/ketan-16/fileflash.git
cd fileflash

# Install dependencies with uv
uv sync

# Run the development server
uv run uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload

Windows (PowerShell):

# Clone the repository
git clone https://github.com/ketan-16/fileflash.git
cd fileflash

# Install dependencies with uv
uv sync

# Run the development server
uv run uvicorn app.main:app --host 0.0.0.0 --port 8000 --reload

Open http://localhost:8000 in your browser.

Mode 2: Build & Run Your Own Docker Image

For custom deployments and self-hosted setups.

Mac/Linux:

# Clone the repository
git clone https://github.com/ketan-16/fileflash.git
cd fileflash

# Build the image
docker build -t fileflash .

# Run with volume mount for persistent storage
docker run -d \
  -p 8000:8000 \
  -v /path/to/files:/app/data/files \
  --name fileflash \
  fileflash

Windows (PowerShell):

# Clone the repository
git clone https://github.com/ketan-16/fileflash.git
cd fileflash

# Build the image
docker build -t fileflash .

# Run with volume mount for persistent storage
docker run -d `
  -p 8000:8000 `
  -v C:\path\to\files:/app/data/files `
  --name fileflash `
  fileflash

Optionally use docker-compose.yml for a simpler setup:

docker-compose up -d

Mode 3: Use Pre-Built Docker Image

Fastest way to get started — no building required.

Mac/Linux:

# Pull the latest image from Docker Hub
docker pull ketan16/fileflash

# Run the container
docker run -d \
  -p 8000:8000 \
  -v /path/to/files:/app/data/files \
  --name fileflash \
  ketan16/fileflash

Windows (PowerShell):

# Pull the latest image from Docker Hub
docker pull ketan16/fileflash

# Run the container
docker run -d `
  -p 8000:8000 `
  -v C:\path\to\files:/app/data/files `
  --name fileflash `
  ketan16/fileflash

All modes will serve the app at http://localhost:8000 with persistent file storage.

⚙️ Configuration

All settings are controlled via environment variables:

Variable Default Description
FILES_ROOT /Users/ketanyadav/Desktop/Projects/fileflash/data/files Directory to store uploaded files
MAX_UPLOAD_MB 512 Maximum file size in megabytes
CHUNK_SIZE_BYTES 1048576 (1MB) Upload chunk size in bytes for streaming
ENABLE_DOCS false Enable Swagger API documentation at /docs

Example Configuration

# Larger upload limit, custom storage
export FILES_ROOT=/mnt/shared-files
export MAX_UPLOAD_MB=2048
export CHUNK_SIZE_BYTES=5242880  # 5MB chunks
export ENABLE_DOCS=true

uv run uvicorn app.main:app --host 0.0.0.0 --port 8000

📡 API Reference

Health Check

GET /healthz

Returns {"status": "ok"} for monitoring and load balancer health checks.

List Files

GET /api/files

Returns all files in storage with metadata:

{
  "items": [
    {
      "name": "document.pdf",
      "size": 1048576,
      "modified_at": "2026-02-22T10:30:00+00:00"
    }
  ],
  "cached_at": "2026-02-22T10:35:00+00:00"
}

Upload File

POST /api/files
Content-Type: multipart/form-data

file=<binary data>

Returns 201 Created with file metadata:

{
  "name": "newfile.txt",
  "size": 12345,
  "modified_at": "2026-02-22T10:35:00+00:00"
}

Error Responses:

  • 409 Conflict - File already exists
  • 413 Payload Too Large - Exceeds MAX_UPLOAD_MB limit
  • 422 Unprocessable Entity - Invalid filename

Download File

GET /api/files/{name}

Downloads file as attachment (forces download dialog).

View File Content (Inline)

GET /api/files/{name}/content

Returns file with inline content-disposition. Useful for viewing images, PDFs, and videos directly in the browser.

Rename File

PATCH /api/files/{name}
Content-Type: application/json

{"new_name": "newname.txt"}

Returns 200 OK with updated file metadata.

Error Responses:

  • 404 Not Found - Source file not found
  • 409 Conflict - Destination file already exists
  • 422 Unprocessable Entity - Invalid filename

Delete File

DELETE /api/files/{name}

Returns 204 No Content on success.

Error Responses:

  • 404 Not Found - File not found

🧪 Testing

Run the test suite:

# Install dev dependencies and run tests
uv run --group dev pytest

# With verbose output
uv run --group dev pytest -v

# Run specific test file
uv run --group dev pytest tests/test_api.py

Test Coverage

  • Upload success and duplicate detection
  • File size limit enforcement
  • Listing with proper sorting
  • Download exact bytes retrieval
  • Rename and delete operations
  • Filename validation
  • Content-type detection

🏗️ Architecture

Backend (Python/FastAPI)

  • Lightweight Framework - Minimal overhead, excellent for LAN scenarios
  • Dependency Injection - Clean, testable API endpoint handlers
  • Type Hints - Full PEP 585 type annotations for IDE support
  • Local File Storage - Direct filesystem operations with atomic moves

Frontend (Vanilla JavaScript + Tailwind CSS)

  • Zero Build Step Required - Load Tailwind via CDN, ship JavaScript as-is
  • Service Worker - Offline caching and resource management
  • IndexedDB - Persistent offline queue for operations
  • Responsive CSS - Mobile-first design with Tailwind utilities
  • External Libraries - PhotoSwipe (images), Plyr (video/audio), PDF.js (PDFs)

File Organization

fileflash/
├── app/
│   ├── __init__.py
│   ├── main.py          # FastAPI app creation, routes setup
│   ├── api.py           # RESTful endpoints
│   ├── config.py        # Environment configuration
│   ├── schemas.py       # Pydantic models
│   └── storage.py       # File storage backend
├── static/
│   ├── index.html       # Main PWA shell
│   ├── app.js           # Frontend logic, API client
│   ├── sw.js            # Service worker
│   ├── manifest.webmanifest  # PWA manifest
│   └── icons/           # App icons
├── tests/
│   ├── test_api.py      # API endpoint tests
│   └── test_web.py      # Web integration tests
├── data/files/          # Default file storage
├── Dockerfile           # Container image
├── docker-compose.yml   # Production deployment
├── pyproject.toml       # Python dependencies
└── README.md            # This file

🔒 Security Notes

Design Philosophy

FileFlash is intentionally unauthenticated and designed for trusted local networks only. There is no built-in authentication, authorization, or encryption.

⚠️ DO NOT

  • Expose directly to the public internet without a reverse proxy and authentication layer
  • Use in untrusted networks without additional security measures
  • Store sensitive or confidential files without network-level security

✅ DO

  • Use on private LANs (home networks, office networks)
  • Deploy behind a VPN or private network boundary
  • Use with organizations that trust internal networks
  • Add authentication via reverse proxy (nginx, Caddy, Traefik) if needed

Implemented Safeguards

  • Filename Validation - Blocks directory traversal attempts
  • Size Limits - Prevents disk exhaustion
  • Atomic Operations - No partial file writes on failure
  • Temp File Cleanup - Removes incomplete uploads

🎯 Use Cases

Home Networks

  • Share files between family computers
  • Media server for photos, videos, documents
  • Backup and recovery playground

Office LAN

  • Team file sharing without external cloud
  • Quick file exchange in workgroups
  • Temporary file hosting for presentations

Lab & Development

  • Edge computing file distribution
  • Docker image/artifact sharing
  • Build artifact repository

IoT & Embedded

  • File management on Raspberry Pi or similar
  • Remote device configuration uploads
  • Local data collection and retrieval

🛠️ Development

Project Setup

Mac/Linux:

# Clone and enter directory
git clone <repo>
cd fileflash

# Create virtual environment with uv
uv sync

# Activate environment
source .venv/bin/activate

Windows (PowerShell):

# Clone and enter directory
git clone <repo>
cd fileflash

# Create virtual environment with uv
uv sync

# Activate environment
.venv\Scripts\Activate.ps1

Running Examples

Mac/Linux:

# Development with auto-reload
uv run uvicorn main:app --reload

# With Swagger docs enabled
ENABLE_DOCS=true uv run uvicorn main:app --reload

# Custom file root
FILES_ROOT=/tmp/files uv run uvicorn main:app --reload

# Production (no reload, optimized)
uv run uvicorn main:app --host 0.0.0.0 --port 8000 --workers 4

Windows (PowerShell):

# Development with auto-reload
uv run uvicorn app.main:app --reload

# With Swagger docs enabled
$env:ENABLE_DOCS="true"; uv run uvicorn app.main:app --reload

# Custom file root
$env:FILES_ROOT="C:\temp\files"; uv run uvicorn app.main:app --reload

# Production (no reload, optimized)
uv run uvicorn app.main:app --host 0.0.0.0 --port 8000 --workers 4

Code Quality

The project uses:

  • Type Hints - Comprehensive type annotations (tested with Pylance)
  • Validation - Pydantic models for request/response validation
  • Unit Tests - pytest for API and storage logic
  • Error Handling - Custom exception hierarchy for clear error messages

📦 Dependencies

Core

  • fastapi ~0.129.2 - Web framework
  • uvicorn ~0.41.0 - ASGI server
  • python-multipart ~0.0.20 - Multipart form handling

Development (Optional)

  • pytest ~8.4.2 - Testing framework
  • httpx ~0.28.1 - Async HTTP client for tests

The entire stack is minimal by design—only 3 production dependencies!

📈 Performance

  • Startup Time - <1 second on modern hardware
  • List Speed - O(n) filesystem scan, typically <50ms for 10k files
  • Upload Speed - Limited by network and disk I/O, handles gigabit LANs efficiently
  • Memory Usage - <50MB baseline, scales with concurrent operations

🐛 Troubleshooting

"Permission denied" on data/files

Mac/Linux:

# Ensure directory is writable
chmod 755 data/files

Windows (PowerShell):

# Right-click folder → Properties → Security → Edit
# Or use icacls to modify permissions
icacls "data\files" /grant:r "%username%:(OI)(CI)F"

Service worker not updating

// Force service worker refresh in browser console
navigator.serviceWorker.getRegistrations().then(regs => 
  regs.forEach(reg => reg.unregister())
);

Upload fails over LAN

  • Check firewall rules allow port 8000 (or configured port)
  • Ensure MAX_UPLOAD_MB is set appropriately
  • Verify disk space on FILES_ROOT

Docker permission issues

Mac/Linux:

# Run with user ID matching your user
docker run --user $(id -u):$(id -g) -v /path/to/files:/app/data/files fileflash

Windows (PowerShell):

# Ensure Docker Desktop is running and volume is accessible
# Windows typically doesn't require user ID specification
docker run -v C:\path\to\files:/app/data/files fileflash

📄 License

This project is licensed under the MIT License. See LICENSE file for details.

🤝 Contributing

Contributions are welcome! Areas for enhancement:

  • Additional media viewer integrations
  • Search/filter functionality
  • File organization (folders/tags)
  • Advanced offline sync strategies
  • i18n support
  • Rate limiting and request throttling

Please open an issue or submit a pull request.

📞 Support

For bugs, feature requests, or questions:

  1. Check existing GitHub Issues
  2. Create a new issue with detailed description
  3. Include your OS, Python version, and reproduction steps

⚡ Quick Tips

Mobile Installation

  1. Open FileFlash in mobile browser
  2. Tap "Share" → "Add to Home Screen" (iOS) or tap menu → "Install app" (Android)
  3. App works offline with queued sync on reconnect

Network Discovery

  • Use your computer's IP (e.g., 192.168.1.100:8000) to access from mobile devices
  • Find your IP:
    • Linux: hostname -I
    • Mac: ifconfig | grep "inet " (or System Preferences → Network)
    • Windows: ipconfig (look for IPv4 Address)

Reverse Proxy (for authentication/SSL)

location /files {
    proxy_pass http://localhost:8000;
    auth_basic "Restricted";
    auth_basic_user_file /etc/nginx/.htpasswd;
}

Built with ❤️ for fast, simple file sharing on local networks.

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A lightweight, self-hosted, high-performance file-sharing application optimized for local area networks (LANs)

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FileFlash v1.0.0 - Official Release Latest
Feb 22, 2026

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