We write a lot about the growth in the number of APIs on ProgrammableWeb. But how about usage? Some APIs see so many requests that they measure in billions. We refer to these companies as the API Billionaires Club. The image below, which comes from ProgrammableWeb Founder John Musser's talk later today at Glue, shows the big names that make up this exclusive club (update: the APIs State of the Market 2011 slides are up now).
All of Twitter's official applications use its API, including Twitter's web client. So, naturally the 140 character service tops the list with 13 billion API calls per day. In addition to its internal use, Twitter is one of the best examples of a vibrant developer ecosystem, despite complaints from some that Twitter is squeezing out the force that made it popular.
Google's spot on the list perhaps puts a scale on Twitter's achievements. The 5 billion calls per day to the search giant is spread amongst the 88 Google APIs. There's likely little internal use of Google APIs, so from a pure external developer standpoint the number of calls to Google is astounding.
Facebook gets a lot of guff for its lack of openness, with many calling it a walled garden. Though the complaints still exist, they were quieted with last year's introduction of the Facebook Graph API, which provides access to much of the content created and shared on the worldwide social network. However, Facebook has been a member of the API Billionaires Club since before its opened graph, showcasing the longtime reach of its developer network.
Other API Billionaires may only measure in billions per month, but its as impressive given their own scale. Hardly a Google or Facebook, NPR used its API and the 1.1 billion API-delivered stories to double its web traffic. The single Netflix API supports hundreds of devices. And the Salesforce.com API, which makes up 50% of the company's traffic, is often credited with the Software-as-a-Service pioneer's success.
The API Billionaires Club, like the growing number of APIs, provides important stories of success. These stories will encourage continued growth of APIs--in both numbers and usage--as mainstream companies continue to pick up on what we've all known for at least six years: the web is not just another channel for our messages. The web is a platform upon which the future is being built.