Fixer.io
Fixer.io is one of the most widely used foreign exchange rate APIs in the developer community, providing real-time and historical exchange rate data for over 170 currencies with a track record of reliability that has made it a trusted foundation for thousands of commercial financial applications globally. Built and maintained by APilayer, Fixer.io has evolved from a simple ECB rate proxy into a comprehensive FX data service aggregating rates from financial data providers with global coverage.
The API provides a latest rates endpoint that returns current exchange rates for all supported currencies against a specified base currency. On the free plan, EUR is the only available base currency — reflecting Fixer.io's origins as an ECB rate service — but paid plans unlock any currency as base including the Nigerian Naira, US Dollar, British Pound, and all other supported currencies. For Nigerian applications where showing Naira as the base currency matters for user experience, upgrading to a paid plan enables NGN-based rate tables that are immediately intuitive to Nigerian users.
Historical rates are accessible through a date parameter that retrieves the exchange rates that were in effect on any past date. Fixer.io maintains an extensive historical database covering many years of past rates, enabling applications to reconstruct the Naira exchange rate history, calculate the cost of historical foreign currency transactions, or build trend analysis features. Nigerian accountants and financial controllers preparing comparative financial statements need accurate historical rates for the periods being compared, and Fixer.io provides this data reliably.
The time-series endpoint enables querying exchange rates across a date range, returning rates for each day between the start and end dates in a single API response. This time-series data powers trend charts, moving average calculations, and volatility analysis. For Nigerian financial professionals analyzing currency trends to inform hedging decisions or procurement timing, time-series data provides the raw material for meaningful analysis without requiring day-by-day API queries.
The fluctuation endpoint is a unique Fixer.io feature that returns the change in exchange rates between two dates, expressing both absolute change and percentage change for each currency. For Nigerian import businesses monitoring how the Naira has moved against supplier currencies over a given period, the fluctuation endpoint provides a direct comparison without requiring the client application to calculate differences from raw rate data.
Currency conversion is directly supported through a dedicated convert endpoint that accepts source and target currency codes and an amount, returning the converted value calculated at current rates. This endpoint streamlines implementation for applications where only the final converted amount is needed rather than access to the underlying rate data.
Fixer.io is available through a freemium model where the free plan provides access to the core functionality with EUR as the only base currency. Professional plans unlock additional base currencies including NGN, increase request frequency, and enable access to historical data, time-series, and fluctuation endpoints. The pricing is transparent and competitive with comparable FX data services, making it accessible for Nigerian fintech startups at various stages of growth.
Nigerian payment processors, fintech platforms, accounting software vendors, and e-commerce developers have deployed Fixer.io as the exchange rate data backbone for their products. The API's extensive documentation, code samples in multiple languages, and the large developer community means that integration questions have usually already been answered in forums and documentation. API key authentication with straightforward query parameters and consistent JSON responses makes Fixer.io one of the fastest currency APIs to integrate into new Nigerian applications.