Pricing-deflector

Inspiration

Dynamic pricing often punishes loyal customers. We noticed consumers were being charged a hidden "tax" based on their browsing history or device type, and wanted to build a tool that exposed this without sacrificing user privacy.

What it does

Price Deflector silently compares the personalized price you see on Amazon, Flipkart, or Airbnb against a clean, anonymous baseline (as well as Android and iOS device profiles). If you are being overcharged, it immediately alerts you via an in-page toast.

How we built it

It's a pure Manifest V3 Chrome Extension with no backend. We use declarativeNetRequest to spoof mobile User-Agents, an Offscreen Document to safely parse background HTML, and injected Content Scripts with MutationObservers to handle dynamic pricing changes and SPA navigation

Challenges we ran into

Bypassing retailer anti-bot protections purely on-device was difficult. We had to build a sequential queue to prevent race conditions with DNR session rules, and circumvent Airbnb's strict CORS policies by routing GraphQL queries directly through the active content script.

Accomplishments that we're proud of

We achieved 100% local, on-device price comparison. The extension requires zero external APIs, no proxies, and no user accounts—guaranteeing total privacy while saving users money.

What we learned

We mastered the intricacies of Chrome's Manifest V3 architecture—specifically managing background service worker lifecycles, safely cleaning up offscreen documents, and standardizing messy JSON-LD/DOM data into actionable numbers.

What's next for Pricing-deflector

A Shrinkflation Tracker to locally alert users when product weights drop while the price stays the same.

Built With

• manifestv3