Domain Watcher | Domain Availability Monitor & Expiration Tracker

Keywords: domain monitor • domain checker • whois lookup • ssl certificate tracker • domain expiration alerts • sveltekit • cloudflare workers • slack notifications • resend notifications • email notifications

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Monitor domain availability, track expiration dates, and get notifications when domains become available or are about to expire.

A modern domain monitoring tool built with SvelteKit and Cloudflare Workers that tracks domain availability, SSL certificates, and sends smart notifications via Slack or email (Resend).

Perfect for: Domain investors, web developers, businesses tracking competitor domains, and anyone managing domain portfolios.

Tech Stack

• Frontend: SvelteKit
• Platform: Cloudflare Workers
• Database: Cloudflare D1 (SQLite)
• Notifications: Slack Webhooks, Resend API
• Scheduling: Cloudflare Cron Triggers
• Domain API: WhoisJSON (1000 free calls/month)

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Table of Contents

• 👀 Overview
• 🚀 Features
• 📦 Setup
• 🛠️ Development
• 🌐 Deployment
• 🗃️ Database Schema
• 🐛 Troubleshooting

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👀 Overview

A SvelteKit application running on Cloudflare Workers that monitors domain availability and sends notifications via Slack or Email (Resend) when domains become available.

In addition to available domains, you also receive:

• A list of domains that are expiring within 30 days
• A list of domains that have already expired but are still registered

A daily summary keeps you informed and helps you act fast.

App Overview

Settings Page

Slack Notification

Email Notification

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🚀 Features

• Domain Monitoring: Monitor domain status, including availability, nameservers (NS), and SSL certificate validity.
• Automated Checks: A cron job runs every minute to evaluate if notification conditions are met (via Slack or Resend), based on the configured time and settings.
• Notifications via Slack or Email (Resend): Get notified when domains become available or when specific conditions are met. Choose your preferred notification method (Slack or Email) and configure when alerts should be sent.
• Settings Panel: Configure API key for WhoisJSON, choose your preferred view mode for the interface, and manage notification settings for Slack and Resend.
• Web Interface: A clean and functional UI where you can add new domains, view and manually refresh domain status, perform bulk checks, and manage your domain list with ease.

📦 Setup

Prerequisites

• Node.js and pnpm
• Cloudflare Account
• WhoIs JSON API key - Get your API key for domain lookups
• Slack Webhooks – Create a Slack app and generate an incoming webhook URL for Slack notifications
• Resend API – Generate your Resend API key to enable email notifications

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🛠️ Development

Local Development Setup

1. Environment Configuration

   Create a local .env file by duplicating the example:

   # Copy the example environment file
   cp .env.example .env

   Then edit .env with your specific values:

   PUBLIC_ENVIRONMENT=dev
   PUBLIC_TIMEZONE=Europe/Ljubljana
   CRON_SECRET=dev-super-secure-key
   PRODUCTION_DOMAIN=https://your-app.com

2. Local Database Setup

   Create and configure your local development database:

   # Creation of DB and applying schema to local database
   npx wrangler d1 execute local-domain-watcher --local --file=./schema.sql

3. Verify Database Setup

   Check that your database was created successfully:

   # Verify local database connection
   npx wrangler d1 execute local-domain-watcher --local --command="SELECT * FROM domains;"

   Expected output: Existing test data

4. Start Development Server

   Launch the local development server:

   # Start development server
   pnpm run dev

   Your application will be available at: http://localhost:5173

Local Build

1. Build the application:

   pnpm run build

2. Start local development server:

   npx wrangler dev --local

3. Test with cron jobs:

   npx wrangler dev --test-scheduled

Testing Cron Jobs Locally

Manual Trigger

Visit the following URL to manually trigger a cron job:

http://localhost:8787/__scheduled?cron=*+*+*+*+*

Expected Console Output

🚀 Starting cron...
🕐 Check at: 21:23

📝 Note: If you see "✅ Local - Self-call completed successfully!" in the logs, it means the local cron function is running successfully.

Cron Schedule

The cron job runs every minute to check scheduled notifications. Since you can set specific times in Slack or Resend settings (e.g., "Send at 14:30"), the cron job must check every minute to trigger notifications at the exact scheduled time.

Example: If notification is set for 14:30, the cron job checks every minute until it matches 14:30, then sends the notification.

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🌐 Deployment - Via Cloudflare with GitHub Integration

Deploy your application using Cloudflare Worker with GitHub integration.

Step 1: Database Setup (Production)

⚠️ Important: Complete database setup before deploying your application!

1.1. Create Production Database

# Connect to CF account and create production database
npx wrangler d1 create prod-domain-watcher

1.2. Update Database Configuration

After creating the database, copy the generated d1_databases configuration into your wrangler.jsonc file under env.production.d1_databases:

"d1_databases": [
    {
      "binding": "DB",
      "database_name": "prod-domain-watcher",
      "database_id": "generated-id"
    }
  ]

1.3. Apply Database Schema

# Apply schema to production database
npx wrangler d1 execute prod-domain-watcher --remote --file=./schema.sql

1.4. Verify Database Setup

# Check if tables were created successfully
npx wrangler d1 execute prod-domain-watcher --remote --command="SELECT * FROM domains;"

Step 2: Create Cloudflare Worker Project:

1. Go to Cloudflare Dashboard:

• Navigate to Workers & Pages under Compute (Workers)
• Click Create → Workers
• Select Connect to Git

2. Import Repository:

• Choose your repository (e.g., "domain-watcher")
• Enter your project name

Step 3: Build Configuration:

• Build command: pnpm run build

• Deploy command: npx wrangler deploy --env production

• Build variables:

  Set these environment variables (update timezone and generate your own secret):

  PUBLIC_ENVIRONMENT = production
  PUBLIC_TIMEZONE = Europe/Ljubljana         # Change to your timezone (e.g., America/New_York, UTC)
  CRON_SECRET = strong-secret-key-here       # Replace with a secure random string (32+ characters)
  PRODUCTION_DOMAIN = https://your-app.com   # Live application URL for email assets and robots.txt control
  ALLOW_ROBOTS = false                       # Set to true ONLY when ready for search engine indexing

⚠️ Important: The CRON_SECRET environment variable must be identical to the value set in your wrangler.jsonc configuration file under env.production.vars.CRON_SECRET!

Step 4: Create & Deploy

• Push to Repository: Commit and push your changes to trigger automatic deployment
• Monitor Build: Check build logs in Cloudflare Pages dashboard
• Verify Deployment: Visit your deployed URL to confirm everything works

Post-Deployment Setup (if needed)

Set Environment Variables in Cloudflare Worker Dashboard:

• Go to Settings > Build > Variables and Secrets
• Add PUBLIC_ENVIRONMENT, PUBLIC_TIMEZONE, PRODUCTION_DOMAIN, CRON_SECRET and ALLOW_ROBOTS

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🗃️ Database Schema

The application uses two main tables:

domains Table

• Stores domain names and availability status
• Tracks domain expiration dates and check history
• Stores complete API responses from WhoisJSON (domain, DNS, SSL data)
• Includes error logging and check statistics

settings Table

• Category-based configuration storage (api, ui, notifications)
• JSON-based config data for flexible settings management
• Handles API credentials, UI preferences, and notification settings
• Supports enabled/disabled states for notification services

For detailed table structure and relationships, see schema.sql

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🐛 Troubleshooting

Common Issues

1. "Database not found": Ensure you've created the database and updated the database_id in wrangler.jsonc
2. "Environment variables missing": Set PUBLIC_ENVIRONMENT, PUBLIC_TIMEZONE, CRON_SECRET and ALLOW_ROBOTS in Cloudflare Dashboard
3. Cron jobs not working: Ensure CRON_SECRET values are identical in wrangler.toml and Cloudflare Dashboard Variables and Secrets
4. Cron jobs not working locally: Use npx wrangler dev --test-scheduled and test via the /__scheduled endpoint

Debugging

• Check logs in Cloudflare Dashboard under Functions > Logs
• Use console.log statements in your code for debugging
• Test API endpoints manually using curl or browser developer tools

Check if your database is set up correctly:

### LOCAL ###
# Check database
npx wrangler d1 execute local-domain-watcher --local --command="SELECT * FROM domains";

# Check database structure
npx wrangler d1 execute local-domain-watcher --local --command="PRAGMA table_info(domains);"

# Export database backup
npx wrangler d1 export local-domain-watcher --local --output=backup.sql


### PRODUCTION ###
# Check production database
npx wrangler d1 execute prod-domain-watcher --remote --command="SELECT * FROM domains";

# Check database structure
npx wrangler d1 execute prod-domain-watcher --remote --command="PRAGMA table_info(domains);"

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Test locally with npx wrangler dev
5. Submit a pull request