Apple is often credited for defining a new class of consumer device with the iPad, which shaped the commercial market for tablets in the following years, and was the most successful tablet at the time of its release. iPads and competing devices were tested by the US military in 2011 and cleared for secure use in 2013. Its debut in 2010 pushed tablets into the mainstream. Samsung's Galaxy Tab and others followed, continuing the trends towards the features listed above. In March 2012, "PC Magazine" reported that 31% of U.S. Internet users owned a tablet, used mainly for viewing published content such as video and news. The top-selling line of devices was Apple's iPad with 100 million sold between its release in April 2010 and mid-October 2012, but iPad market share (number of units) dropped to 36% in 2013 with Android tablets climbing to 62%. Android tablet sales volume was 121 million devices, plus 52 million, between 2012 and 2013 respectively. Individual brands of Android operating system devices or compatibles follow iPad with Amazon's Kindle Fire with 7 million, and Barnes & Noble's Nook with 5 million.