B3 Quick Quote

About the project

B3 Quick Quote is a Google Chrome extension for checking Brazilian stocks and real estate investment funds (FIIs) traded on B3 without leaving the current browser page.

Problem

Looking up a quote can mean switching between the browser, a brokerage platform and financial websites. For a quick price check, these extra steps interrupt the task at hand.

Solution

Users click the extension icon and enter a ticker to view its price, change and daily trading data. The extension also displays the top gainers and losers among tracked assets and lets users set price alerts.

My role

I designed and built the product, from the extension architecture to its release on the Chrome Web Store. I implemented the market data API integration, alert system, interface, and free and Pro features.

Key features

• Stock and FII lookup by ticker
• Price, percentage change and change in Brazilian reais
• Daily opening price, high, low and trading volume
• Top gainers and losers among tracked assets
• Market status and last update time
• Price alerts with browser notifications
• Recall of the last asset viewed
• Free and Pro plans

Architecture and technical decisions

The extension uses plain JavaScript and Manifest V3. This keeps the package small and supports fast access to the quote popup.

API calls run in the service worker, which normalizes responses before passing them to the interface. The gainers and losers ranking is cached for 30 seconds to reduce repeated requests when the popup is reopened.

A Chrome alarm checks prices in the background every 3 minutes. Each alert includes an asset, a target price and a trigger condition, above or below that price. A minimum interval of 60 minutes between notifications for the same alert prevents repeated messages when a price fluctuates around the threshold. Each user can keep up to 3 active alerts.

Technical challenges

• Communicating delayed quotes. The update time and market status help users interpret the data returned by the API.
• Preserving state between runs. Manifest V3 service workers can stop when idle, so alerts and cache data are persisted in extension storage. Periodic checks use Chrome alarms.
• Controlling notification frequency. A per-alert interval limits repeated notifications for the same asset.

Outcome

Published on the Chrome Web Store.

Technologies

JavaScript, Chrome Extensions (Manifest V3), brapi.dev API and CSS.