There are a number of ways to discuss API popularity. One of the common methods ProgrammableWeb has used is by mashups, the number of completed apps. However, there may be a leading indicator before developers have even started writing code. The "track" functionality on ProgrammableWeb lets developers declare an interest in receiving updates on particular APIs. By diving into this data we can see many things. For example, recently developers have loved travel. Overall, social and visual APIs rule.
Top 10 tracked APIs of all time
No surprise here. The biggest social network is the fabric of many of today's applications.
There's nothing like YouTube when you want a repository of engaging content. It's no wonder developers are interested in Google's video service.
The social graph on LinkedIn is very different from Facebook and Twitter. When it comes to business applications, no other API makes as much sense.
7. Amazon Product Advertising
The granddaddy of this list, Amazon understood and applied the power of APIs early on. Its popularity with developers may also be related to paying them when users make purchases.
Still an excellent source of visual content, Flickr is a perennial mashup favorite, too.
10. Google Talk
It's almost hard to remember how proprietary instant messaging was before Google Talk came along and supported XMPP. The open standard and vast Google network clearly appeals to developers.
There are another three weather APIs in the top 20: Weather Channel, Weather Underground and Yahoo Weather. Also, a couple of messaging APIs (MSN Messenger, Skype), a couple of travel APIs (Kayak, Yahoo Travel), two delivery companies (FedEx, DHL) and foursquare round out the popular APIs.
Recently popular: Developers love travel
Among the APIs developers have tracked recently is a combination of the big names from the top 10, travel services and a few outliers.
Travel has a rich API history. Long before we called it an API, the travel industry had a network to connect airlines and agents. Although it's always been a popular category, perhaps travel is poised for more growth in 2014—there are a handful of other travel APIs just outside the top 10 recently tracked APIs.
What's your favorite API on this list? Which ones surprised you?