Twinprice - Currency Converter for Every Page by Krlo

Twinprice shows you what a foreign price costs in your own money, right where the price sits on the page.

Open a shopping page and Twinprice scans it inside Firefox. When it finds a price it recognises, it offers to convert, and shows you the rate before you accept. The converted value appears beside the original, so you keep both numbers and can still see what the shop actually charges.

Nothing about the page leaves your browser. Detection, conversion and rendering all happen locally. The only thing sent to the exchange-rate service is a three-letter currency code such as USD or EUR. Never page content, never prices, never the sites you visit.

WHAT YOU CAN CONVERT

• Every recognised price on a page, in one click
• A single price you highlight, using the right-click menu
• Any amount you type into the popup

CURRENCIES

• Over 160 currencies to convert into, searchable by code or name
• 50 currencies detected automatically from the page, using structured product data, currency codes, symbols and page context
• Currency-native precision, including zero-decimal yen and three-decimal dinar
• Recently used currencies stay at the top

HOW IT LOOKS

• The converted value beside the original, or replacing it
• Choose the text colour, background and corner shape, with a contrast check that tells you whether your choice meets WCAG AA
• Undo restores the page exactly as it was

EVERYDAY USE

• Mark the sites you shop on most to convert automatically
• Prices added later by dynamic and single-page sites are picked up too
• Convert the page with Ctrl+Shift+Y, or Command+Shift+Y on macOS
• The popup shows the current rate and how it has moved over seven days

ABOUT THE RATES

Reference rates come from the Frankfurter service, which publishes European Central Bank rates once per working day. Recent cached rates are used immediately while fresh ones load, are flagged once they pass 48 hours, and are never used beyond seven days.

These are reference rates for comparing prices. They are not the rate your bank or card provider will charge, and they do not include fees or margins.

PRIVACY

Price detection runs on ordinary HTTP and HTTPS pages and happens locally in Firefox. Page contents, highlighted text, price values, visited URLs and browsing history are never sent to the developer or to the rate provider. Only ISO currency codes are sent to Frankfurter.

Twinprice stores your preferences, recent currency choices, cached exchange rates, and only the sites you explicitly approve for automatic conversion. There is no advertising, no analytics, no tracking and no remotely hosted code.

The add-on declares required websiteContent data collection because a source currency code detected from the page can be sent to the rate provider. No raw page text, URL, price amount or browsing history is transmitted.

LIMITATIONS

Prices inside images, closed shadow roots and inaccessible cross-origin frames cannot be converted. Some unusual or heavily scripted price layouts need the source currency chosen manually.

Works on Firefox 140 and newer, and Firefox for Android 142 and newer. Open source under the MIT licence.