This Firefox extension adds a button to your Firefox toolbar, which opens a simple popup displaying the latest info about the stocks you follow.
Stock data is refreshed each time you open the popup. It requires a Financial Modeling Prep API Key.
Followed stocks are set in the extension's options page.
FMP API also supports Forex (e.g. EURUSD) and Crypto (e.g. BTCUSD) data.
Popup code originally inspired by https://github.com/toddwschneider/stocks.