The original vision of ubiquitous computing was for computers to assist humans by providing subtle and fitting technologies in every environment. The iPhone and similar smartphones have provided continuous access to the internet to this end. In the current thesis, my goal was to characterize how the internet is used on smartphones to better understand what users do with technology away from the desktop. Naturalistic and longitudinal data were collected from iPhone users in the wild and analyzed to develop this understanding. Since there are two general ways to access the internet on smartphones—via native applications and a web browser—I describe usage patterns through each along with the influence of experience, the nature of the task and physical locations where smartphones were used on these patterns. The results reveal differences between technologies (the PC and the smartphone), platforms (native applications and the mobile browser), and users in how the internet was accessed. Findings indicate that longitudinal use of web browsers decreased sharply with time in favor of native application use, web page revisitation through browsers occurred very infrequently (approximately 25% of URLs are revisited by each user), bookmarks were used sparingly to access web content, physical location visitation followed patterns similar to virtual visitation on the internet, and Zipf distributions characterize mobile internet use. The web browser was not as central to smartphone use compared to the PC, but afforded certain types of activities such as searching and ad hoc browsing. In addition, users systematically differed from each other in how they accessed the internet suggesting different ways to support a wider spectrum of smartphone users.