Synced

Minimal, privacy-first, real-time file sharing and chat platform built with Node.js and Socket.io. It enables instant sharing and media previews without the need for a database.

Features

Communication

• Real-time text messaging broadcast via WebSockets.
• Dynamic user color assignment based on active session hues.
• Live counter showing the number of connected users.
• Automatic message grouping by sender and timestamp.

File Sharing

• Instant drag and drop file uploads from the desktop.
• Paste support to upload files directly from the clipboard.
• Concurrent upload queue management with a global progress bar.
• Support for large file transfers up to 8GB by default.
• Persistent file access via the uploads directory.

Media and UI

• Integrated preview engine for images, videos, and audio.
• Built-in PDF viewer with mobile-specific fallback links.
• Resizable split-pane layout for simultaneous chat and previewing.
• Fullscreen video support with automatic orientation locking.
• Audio player with seek, progress tracking, and instance management.

Security and Maintenance

• IP-based rate limiting to prevent message and upload spam.
• Disk space monitoring to halt uploads when host storage is low.
• Ephemeral IP anonymization using SHA-256 + random salt hashing.
• Client-side log manager for debugging and troubleshooting.
• Configurable proxy trust settings for secure production headers.

Technical details

• Framework: Built on Node.js 22 using Express 5 and Socket.io 4.
• Database: None. File metadata is derived directly from the filesystem.
• MIME Detection: Uses the file-type library to inspect magic bytes for security.
• Storage: Files are stored with sanitized names and unique prefixes to prevent collision.
• Networking: Supports XHR and Data URL upload methods based on file size.
• Privacy: All IP masking uses a random salt generated at server startup.

Configuration

Settings are managed via the .env file.

Variable	Default	Description
PORT	3000	Port where the application listens.
HOST	127.0.0.1	Host address to bind the server to.
MAX_UPLOAD_MB	8192	Maximum allowed size per file in megabytes.
MAX_USERS	100	Maximum number of concurrent socket connections.
MAX_REQ_PER_MIN_PER_IP	100	Rate limit for socket messages per minute per IP.
PUBLIC_SERVE	true	If true, Node serves static files and uploads.
DISK_RESERVED_MB	1024	Minimum free disk space required for uploads.
TRUST_PROXY	loopback	List of proxy addresses to trust.

Quick start

The recommended way to run Synced is via Docker.

1. Clone the repository.
2. Create your environment file:

cp .env.example .env

3. Create the storage directory:

mkdir uploads
chmod 777 uploads

4. Start the container:

docker-compose up -d

5. Access the application at http://localhost:3000.

Manual installation

Ensure Node.js 22 or later is installed.

1. Install dependencies:

npm install --omit=dev

2. Create the upload directory:

mkdir uploads

3. Start the server:

npm start

Production deployment

For high-performance environments, use Nginx to serve static assets and the uploads directory.

1. Set PUBLIC_SERVE=false in your .env.
2. Configure Nginx:

server {
    server_name share.example.com;
    listen 80;

    root /var/www/synced/public;
    index index.html;

    location /uploads/ {
        alias /var/www/synced/uploads/;
        add_header X-Content-Type-Options "nosniff" always;
        add_header Content-Security-Policy "default-src 'none'; sandbox allow-popups" always;
        add_header Content-Disposition "inline" always;
        access_log off;
    }

    location = /upload {
        client_max_body_size 10G;
        proxy_pass http://127.0.0.1:3000;
        proxy_request_buffering off;
        proxy_read_timeout 3600s;

        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

    location / {
        try_files $uri $uri/ @node;
    }

    location @node {
        proxy_pass http://127.0.0.1:3000;
        proxy_http_version 1.1;
        proxy_buffering off;

        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "Upgrade";
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}