Web Monitor

Monitor web pages for content changes with CSS selector targeting, change detection via hashing, and notification integration. Use for price tracking, content alerts, and website change detection.

Web Monitor — Page Change Detection & Alerts

Track web pages for content changes using hash-based comparison. Supports CSS selector extraction, interval-based monitoring, change history, and configurable notification delivery.

Quick Start

# Compare current page with previous snapshot
python scripts/monitor.py --url https://example.com --compare state.json

# Monitor with a CSS selector
python scripts/monitor.py --url https://example.com --selector ".price" --compare state.json

Usage

python scripts/monitor.py --url URL [OPTIONS]

Options:
  --url URL              Page URL to monitor (required)
  --selector SELECTOR    CSS selector to extract specific content
  --compare FILE         Compare with previous snapshot from FILE
  --state-file FILE      Save current state to FILE (default: state.json)
  --interval SEC         Auto-monitor at interval (seconds)
  --notify COMMAND       Command to run on change detected
  --json                 Output as JSON
  --max-retries N        Connection retries on failure (default: 3)

Examples

# Simple page check
python scripts/monitor.py --url https://example.com/page --compare state.json

# Monitor a price element
python scripts/monitor.py --url https://shop.example.com/product \
  --selector ".product-price" --compare price-state.json

# Continuous monitoring
python scripts/monitor.py --url https://example.com \
  --interval 3600 --compare state.json --notify "echo 'Changed!'"

# JSON output for pipeline
python scripts/monitor.py --url https://example.com --json

State File Format

{
  "url": "https://example.com/page",
  "selector": ".price",
  "hash": "sha256hash...",
  "timestamp": "2026-01-15T14:30:00Z"
}

Features

• Hash-based change detection — reliable content comparison
• CSS selector extraction — monitor specific page sections
• State persistence — stores snapshots for comparison
• Interval monitoring — automatic periodic checks
• Notification hooks — trigger commands on changes
• No external dependencies — uses only Python stdlib
• SSL/HTTPS support — secure page fetching
• JSON output — structured data for automation