FXCM - FXCM is a UK-based Forex Capital Market that offers forex and CFDs trading and a part of Leucadia that is a diversified holding company.

Open Exchange Rates - Free, hourly-updated exchange rates - a simple, accurate, open-source JSON API. Free for personal use, a bargain for everybody else.

OANDA - OANDA is an advanced forex and broker trading platform that helps you in currency data, exchange rate services for the investors and organizations.

exchangeratesapi.io - Foreign exchange rates API with currency conversion.

Avatrade - Avatrade is an online and advanced FX & CFD broker that provides personal investment and trading facilities with the help of currency pairs, cryptocurrencies, commodities & indices as well.

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.