Flutter is the fastest-growing cross-platform framework for mobile development, and currency conversion is one of the most common features in finance, travel, and e-commerce apps. If you are building a Flutter app that needs exchange rate data -- whether for a currency converter widget, a travel budget planner, or a multi-currency shopping cart -- you need a currency API that works cleanly with Dart and the Flutter ecosystem. The challenge: most currency APIs were built for web backends, not mobile apps. They lack Dart packages, provide no guidance on offline caching, and offer free tiers so restrictive that you cannot even test your app properly on a real device. Some return bloated JSON payloads that waste bandwidth on metered mobile connections. This article compares the 5 most popular currency exchange rate APIs for Flutter and Dart in 2026 and shows you exactly how to integrate each one.…