dropwatch

Dropwatch

Watch product prices across any store. Get notified when they drop. 100% local, no tracking.

What it does

Visit a product page on any major retailer, click the Dropwatch icon, and hit Track this. The extension re-checks the price every 6 hours in the background. When the price drops by more than your threshold, you get an OS notification and a badge on the extension icon. Everything stays in your browser.

Works out of the box on any site that ships JSON-LD or Open Graph product markup — which covers most major retailers. Confirmed working on Bol.com, Coolblue, Zalando, H&M, Albert Heijn, and many more.

Features

• One-click tracking from any product page with structured data
• Background price checks every 6 hours — uses your own browser session and cookies so bot-detection treats it like normal browsing
• Drop threshold default 10%, editable per product
• OS notifications + extension icon badge on new lows
• Full local price history (capped at 200 points per product)
• No account, no server, no analytics

Privacy

No data leaves your device. Ever. The only outbound network requests are to product URLs you explicitly chose to track, and only to re-check the price.

See privacy-policy.md for details.

Install

Until the extension is live on the Chrome Web Store, you can load it manually:

1. Clone or download this repo
2. Open chrome://extensions
3. Enable “Developer mode”
4. Click “Load unpacked” → select this folder

Known limitations

Amazon is not supported in v1.0.0. Amazon’s product pages do not ship JSON-LD or Open Graph product markup — they render prices inside DOM elements only. A per-store Amazon extractor is planned for v1.1.

Sites behind aggressive bot detection may return CAPTCHA pages to the background fetch — the extension skips those gracefully. Visiting the page manually refreshes the price.

How it works

• src/popup.js runs when you open the extension. It asks Chrome for activeTab access and runs a short detection script in the current tab that returns the page’s HTML. The parser in src/lib/parser.js then reads any <script type="application/ld+json"> blocks or Open Graph meta tags to normalize the product data.
• When you click Track this, the popup asks Chrome for optional_host_permissions for that store’s origin. On approval it hands off to the service worker in src/background.js, which stores the product and schedules a chrome.alarms entry.
• Every 6 hours (plus a few minutes of jitter), the alarm fires. The service worker fetches the product URL (with your cookies attached thanks to the granted host permission), re-parses the response, appends to the price history, and fires chrome.notifications if the drop crosses your threshold AND the new price is strictly lower than the previously-notified low.

No bundler. Plain JS. MV3. npm test runs Node’s built-in test runner against real and synthetic fixtures.

Contributing

Issues and PRs welcome. This is a hobby project — don’t expect enterprise-grade support, but real bug reports will get real responses.

License

MIT — see LICENSE.

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