So you're interested in the details? Below you will find an elaborated table containing all results and details we could find online and via each provider's customer services. To be fair - each of these currency converter APIs provides great services and data!
This comparison focuses on pricing, data coverage, API functionality, features and user experience. Enjoy our findings.
Alright, let's first talk about data. All of the above currency converter APIs provide (more or less) accurate exchange (forex) rates delivered in easy-to-use file formats. While the number of currencies supported, offered quote types and historical rates (exception: XE) are pretty similar for each one of them, the most significant ratio of difference can be found in data sources and update frequencies.
Customers like to know where the data they are purchasing comes from, which makes it difficult for a service which does not disclose any types of data sources to appear trustworthy. The good news: 4 out of 5 of our APIs did. Currencylayer and the XE API both source their exchange rate data from banks and commercial sources, Oanda gets them from its very own trading platform, and Xignite retrieves real-time forex rates through a number of major financial data vendors.
An equally important factor is how often this data is refreshed. Excuse us, we are really focusing on the details here: the currencylayer API offers the most options to choose from, ranging from 60 minutes to 60 seconds (which is remarkable, considering their low prices), the Open Exchange Rates API lets users choose between 60 minutes and 10 minutes, XE offers daily or 60-second updates, and Xignite and Oanda seem to offer "true" real-time rates, updated almost live as forex trades are happening.
In terms of functionality, we have to mention that the vast majority of features can be considered “convenience features”, since they are all based on the very essential API functionality, which is the delivery of the actual real-time rates, and could be (more or less easily) rebuilt.
Now, each provides an SSL endpoint, the possibility to specify a base currency (which is the currency to which all other currencies are relative to) and to limit the API results to a certain number of currencies. A slight weak spot in API functionality appears for the XE API, which does not seem to support a separate API endpoint for currency conversion, time-series data or any parameters defining the change of a currency rate over a specific period - but as mentioned, these features are not absolutely necessary in order to realise at least a substantial part of a currency converter API's potential.
3 out of 5 APIs deliver their rates in JSON format, which has become the general routine for many REST API services, and 4 out of 5 currency converter APIs deliver their rates as currency pairs, which - as well - has become a standard for reliable forex data providers and makes it easier for the end-user to understand how the data is computed.
Now for the factor that influences most of our decisions, and which also happens to see the largest differences between each provider - the pricing. A clear thumbs-up for both the currencylayer API and Open Exchange Rates for providing an entirely free subscription plan and keeping their prices low in general. The table says more than a thousand words - take a look at it for the most important pricing components.
Although we have done our best researching each currency converter API, we cannot guarantee the content of this website to be entirely correct and free from errors. Any suggestions, comments or complaints? Contact us at [email protected] - we'll get in touch as fast as possible!