The proportion of web survey responses submitted from mobile devices such as smartphones is increasing steadily. This trend presents new methodological challenges because mobile responses are often associated with increased breakoffs, which, in turn, can increase nonresponse bias. Using data from a survey of college students with more than 20,000 respondents, response patterns are examined to identify which days and times the survey invitation and reminder emails were most likely to produce nonmobile responses. The findings provide guidance on the optimal timing for recruiting college student sample members via email to reduce their likelihood of responding from a mobile device, and potentially, breaking off.