Fixer.io - Fixer provides a free, simple, and lightweight API for current and historical foreign exchange rates and currency conversion. The API tracks rates published daily by the European Central Bank.
XE.com - XE.com Inc. (XE) is a Canadian online foreign exchange services company.
FXRatesAPI - Your Gateway to Real-Time Exchange Rates
exRate - exRate is a web application created to help users easily manage their exchange rate alerts.
Freecurrencyapi.com - Freecurrencyapi.com is a free, reliable & feature-complete currency exchange rates API. 32 world currencies & daily update rates.
CurrencyScoop - Developer-friendly REST API with real-time and historical currency exchange rates for world currencies and cryptocurrencies.