Currencia by Minduos

Currencia adds instant currency conversion to Zen/Firefox. Select any price on any web page — "$51.25", "6 499,00 zł", "EUR 1,234.56" — and a small popup shows it converted to your chosen currency right next to your selection.

Features:
• Recognizes major currency symbols ($ € £ ¥ zł kr and more) and ISO codes (USD, PLN, GBP...)
• Handles both US and European number formats (1,234.56 vs 1.234,56)
• Pick any target currency in the settings page
• Turn the feature on/off with one switch
• Toolbar icon flashes briefly to confirm a conversion happened

Rates are fetched from a free, open exchange-rate dataset and cached locally, refreshing once a day. No accounts, no tracking, no personal data collected, everything runs client-side except the daily rate fetch.