Currency Converter Tooltip — KrisLux

Scans any web page for prices denoted with $, €, or £ - either before or after, e.g. "$50" or "50 €", and adds a mouseover popup with the price converted to any local currency you want.

Although it scans through the entire web page, the addon is very fast, typically taking 5-30 milliseconds to scan even heavy websites.

Currently uses ExchangeRate-API.com to get the latest currency rates. No particular reason for this choice, other than they have a free tier that should be enough for everyone.

Note: Prices denoted with $ will be assumed to be USD. Does not currently respond to e.g. AUD or CAD suffixes.