Price Drop Watcher
Remembers what a thing cost when you first looked at it.
What you're making
Add something to a watchlist and this quietly checks the price for you, then tells you when it drops. More usefully, it keeps the history — so when a shop shouts about a big discount, you can see whether the price genuinely fell or just went back to what it always was. It works on whatever sites you teach it.
An extension that captures a price from a page, re-checks it on a schedule, and charts the history. The honest-history angle is what makes it worth building — fake discounts are common and a price chart exposes them instantly.
Hosting · Free forever
Deploys free on Firefox Add-ons or GitHub Releases.
Firefox's store is free. Chrome's charges a one-off developer fee, so ship Firefox first if you'd rather pay nothing.
Free on Firefox Add-ons; Chrome's store charges a one-off developer fee.
Core features · 7
- Capture the price on the current page with one click
- Re-checks watched pages on a schedule
- Charts price history so fake discounts are obvious
- Notifies when a price drops below a target you set
- Works across several sites via configurable selectors
- Tells you clearly when it can no longer find the price
- All data stays on your machine
The interesting part
- Sites change their markup constantly, so extraction breaks and must fail loudly
- Background scheduling in an extension, which the browser may throttle or suspend
- Currency and locale parsing — a comma means different things in different places
Once it works
- Detect the price automatically using structured page data
- Add a lowest-ever badge on the page itself
- Export the history as a spreadsheet