Web surveys are no longer completed on just a desktop or laptop computer. Respondents increasingly use mobile devices, such as tablets and smartphones to complete web surveys. In this article, we study how respondents in the American Life Panel complete surveys using varying devices. We show that about 30 percent of respondents sometimes complete surveys on a mobile device, and about 12 percent always use a mobile device. We study the characteristics of these “mobile-only” web survey respondents, and find that they share many characteristics of typically hard-to-recruit survey respondents. They are more likely to be non-white, young, and not have a higher education. In terms of voting behavior we find no differences between the groups of survey respondents who use different devices. This suggests that biases in political polls conducted through web-surveys are unlikely to occur when mobile-only respondents are underrepresented.