Smartphone ownership has steadily increased since 2011 and accordingly so has the use of mobile applications or “apps”. The use of the internet for surveys has risen as well, with about a fifth of general population web surveys now being taken on mobile phones. A logical next step is to see whether we can marry the two trends, moving web surveys from a browser to an app on mobile phones. However this approach raises questions as to whether respondents would be willing to download an app and actually use it, and how the data collected via an app differs from data collected from a web browser survey on mobile. To answer these questions the Pew Research Center conducted an experiment that randomly assigned 2,146 members of a survey panel to receive a series of short surveys either on a mobile app or on a mobile browser. Of those invited, 91% have agreed to participate. The sample source for this experiment was the Pew Research Center’s American Trends Panel, a nationally representative probability-based panel. This experiment used a signal-contingent experience sampling method to survey respondents twice a day for seven days about their smartphone use. Panelists were signaled via text message and email for both the mobile browser and app groups, as well as push notification for the app group. The study is in the field at this time and will be completed in November. Willingness to download the app will be examined as will response rate, non - response bias, and differences in substantive responses by treatment group. In addition to tabular comparisons of cooperating and non-cooperating groups, a multivariate analysis of the factors predicting consent and cooperation will be conducted.