Valuable insights can be gained by applying visual analytic techniques to understand complex, emerging ecosystem dynamics and evolving enterprise strategies.1,2 One such context is the application programming interface (API) ecosystem. APIs have grown dramatically in the past five years. These bits of code act as digital control points that set the terms for which data and services can be efficiently shared or "called" over the Internet.11 There are now over 12,000 open APIs available across a wide range of market sectors, a thirtyfold increase since 2006.a While the ability to connect to digital resources using APIs has been a feature of computing for decades, the prominence of digital platforms, the rise of mobile computing, lower cost of data storage, and just the sheer usefulness of automating how digitally encoded information can be made available and exchanged has helped to spur faster growth. Some of the most popular APIs handle a staggering number of calls. For example, Twitter, Google, Facebook, Netflix, AccuWeather, eBay, and Sabre all handle over a billion API calls per day.4
Firms are finding APIs to be beneficial in a variety of ways. The initial provider can use an API as a way to create new revenue streams, by offering access to already existing digital information through a range of different business models (including subscription, license, freemium, or pay-as-you-go). For example, Thomson Reuters, which has an extensive 45 million over-the-counter exchange-traded instruments globally, is building out a set of APIs to make it easier for other companies to access this data.3 APIs also make it possible for third parties to build entirely new digital applications and services by creating "mashups" that integrate existing APIs. More than 6,000 such mashups have been created in recent years.