The zettabyte is now the largest unit of digital measurement. A zettabyte is equal to 1 billion terabytes and 1 million petabytes or 1,000,000,000,000,000,000,000 individual bytes. It is a measure of storage capacity. The total amount of digital content produced by humans is 8 million petabytes, which is expected to rise to 1.2 zettabytes.
In fact, the current size of digital content in the world is comparable to all the data that can be stored on 75 billion Apple iPads. This rapid growth is caused by the sudden increase of social networking websites, online video, digital photography and mobile phones. According to the most recent figures in the annual survey of the world's digital output by IDC, a technology consultancy, around 70% of digital content produced by individuals is stored on content sharing websites like YouTube. The first survey in 2007 projected that the digital universe was equal to 161,000 petabytes. But since then, the types of media and the number of devices through which information can be generated and stored has increased. As a result, the unit of digital measurement has also been expanded to zettabyte.