MonMon

MonMon is a small Python 3 console app that monitors websites for changes and alerts you both in the terminal (with colored diffs) and via a Discord webhook. You can watch the entire page or just a specific CSS selector (like you would copy from your browser’s Inspect tool). Optional JS-rendered fetching is available for dynamic pages via Playwright.

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Features

• Monitor the whole page or a CSS selector (e.g. .result-item, #main, div.card > h2).
• Two compare modes:
  • text (DOM text content) — resilient to cosmetic HTML churn.
  • html (raw node HTML) — detects precise markup changes.
• Discord webhook alerts with unified diffs; console shows colored diffs.
• Selector preview when adding a monitor (accept/adjust before saving).
• Optional JS-rendered mode using Playwright for SPA/dashboards.
• ETag/Last-Modified support to reduce bandwidth and avoid noisy checks.
• Optional heartbeat status that prints “checked, no change”.
• Preset User-Agent selection (Windows, macOS, Linux, mobile, etc.).
• Saves full diffs to diffs/ when a message has to be truncated.

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Requirements

• Python 3.8+
• Packages: requests, beautifulsoup4
• Optional (for JS-rendered pages): playwright and the Chromium runtime.

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First-time setup

1. Choose 2) Set Discord webhook and paste your webhook URL.
2. Choose 1) Manage Monitors and follow the prompts:
   • Enter the target URL.
   • Enter a CSS selector or press Enter to watch the whole page.
   • Pick text or html mode.
   • Choose your check frequency in seconds.
   • Optionally provide a custom User-Agent for this monitor.
   • For dynamic pages, enable JS-rendered mode and configure the wait time/selector.
   • If you provided a selector, review the preview and accept or refine it.
3. Choose 3) Start monitoring.

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What exactly gets monitored?

• Whole page: Leave the selector blank to compare the entire HTML (or its text) each run.
• CSS selector: Enter something like .of-search-domain-result-item__wrapper. The app selects all nodes that match and concatenates their extracted content in document order.
  • In text mode, it uses each node’s visible text (descendants included).
  • In html mode, it uses the raw HTML for each matched node (descendants included).
  • Narrow your selector for tighter scope (e.g. div.card > h2 vs div.card).

If a selector matches nothing, the app warns in the console during preview and monitoring.

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Alerts and Diffs

• Console: On change, the app prints a [CHANGE HH:MM:SS] line, the URL, and a colored unified diff.
• Discord: Sends an embed titled “Website Change Detected” with the URL, selector, mode, and a unified diff. If the message exceeds Discord’s limits, the app writes the full diff to diffs/<timestamp>_<id>.diff.txt and indicates that path in the embed.
• Timestamps: Change alerts include a timestamp in the console and as a footer in Discord embeds.
• Heartbeat: When enabled, the console prints periodic “checked, no change” messages.

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State and Files

• monitor_state.json stores:
  • Discord webhook URL
  • Verbose heartbeat setting
  • Global default User-Agent (if chosen)
  • Monitors and their baselines: last hash, last excerpt (first 2000 chars), ETag, and Last-Modified.
• State writes are atomic to reduce “.json.tmp access denied” issues on Windows.
• Full diffs are written to the diffs/ directory when needed.

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User-Agent Presets

Use menu option 7) Choose default User-Agent (presets) to pick a realistic UA for all monitors. You can still override per monitor when adding it.

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JS-rendered Mode

For sites that rely on client-side rendering (SPAs, dashboards), enable JS mode for a monitor. The app will use Playwright (Chromium) to load the page, wait either a fixed duration or an optional wait_for CSS selector, then capture the HTML for comparison.

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Troubleshooting

• Selector matched no content: Adjust your CSS to a parent wrapper that exists on the page, or verify the page is available without authentication.
• 304 Not Modified: The server indicated nothing changed for the request conditions. The app still compares extracted content when new HTML is received. With 304, you may only see the heartbeat.
• Access errors (4xx/5xx, timeouts): These are shown in the console and also sent to Discord as “Website Access Error.”
• Local/HTTPS issues: For non-public endpoints, ensure the machine running the monitor can reach them and that your URL scheme (http:// vs https://) is correct.
• Too noisy: Switch to text mode, narrow your selector, increase interval_sec, or disable heartbeat.

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Notes

• Use reasonable check intervals to respect target sites.
• Your Discord webhook URL is stored locally in monitor_state.json. Treat it as a secret.
• For large or frequent diffs, rely on the saved files in diffs/ for full context.