The API growth rate continues to double. In 2011, there were 2,031 APIs added to our API directory. Big companies added APIs, including the three major credit card companies in the US. But the biggest story was the continued social API growth. There are also some surprises in this year's list of the most popular API categories and a big upset as for the first time Google Maps API was not the most popular API.
The directory now lists 4,678 APIs, as the open API timeline above shows. Five years ago there were only about 600 350 APIs, which means the directory has grown nearly eight over 13 times its size since 2007.
Top 5 Types of APIs in 2011
Social and internet fill the top two slots, echoing what we saw in the 2010 API stats. Telephony has become a larger part of the directory for likely two reasons. First, telco operators are waking up to the API world. And secondly, the Twilio API has shown everyone the utility of infrastructure-as-a-service.
Reference and government show trends within open data. For governments, it's a trend we've followed for some time. 2009 and 2010 were the years everyone talked about open government. In 2011, it actually happened, as there are now APIs from all levels of government across many countries.
Top 5 APIs by Mashups
In 2011 there were 901 mashups added to our mashup directory. From there we can determine the popular APIs used. Unlike every year prior, this year Google Maps has been usurped by the telephony API trend and the popularity of the Twilio API. In fact, Twilio is also number four.
As we enter 2012, we're preparing for a new wave of APIs. We're certain they'll be great in numbers, but also in the types of companies we see exposing APIs. If last year brought credit card companies, governments and more social than we've ever seen, what will 2012 have in store? Read the expert predictions or let us know your thoughts in the comments.