The lists of monitored APIs consists of 26 of the most heavily trafficked Web services, including Google Search, Google Maps, Bing, Facebook, Twitter, SalesForce, YouTube, Amazon, eBay and others.
API-status.com calls and checks for a valid result on each of the APIs every five minutes from 42 locations across the globe. If the system detects an anomaly or delay of more than four seconds on any of them, the result is registered as an error and the status of the API will get indicated on the website as unavailable. These errors are used to count towards the percentage of availability or uptime for each of the sites.
Details on API-status.com include a seven-day history, along with a 24-hour glance and performance indication by country for each API.
WatchMouse closely monitored the availability of all 26 Web services between December 16th 2009 and January 16th 2010. For the sake of the survey, the startup only selected a single function per API; the most simple one that requires authentication. This means that their survey does not cover an in-depth test of the full APIs, but provides an estimate of the availability and working functionality of each API.
As said, the methodology for testing the sites includes one simple API call and check for a valid result. This typically meant an authentication action, including a login, followed by a search or listing action, plus a check of the expected result action. Each site was checked in real time using the WatchMouse Public Status Pages tool.
WatchMouse found that Yammer's API had the lowest availability of the bunch (with 96.09 percent uptime) while Amazon, Google Maps, Google Search, Last.fm and Yahoo Maps recorded the highest availability with 100 percent uptime. More results here.