The increase in web surveys allows researchers to collect a variety of paradata alongside traditional survey responses. Some paradata, such as response times, enjoy a long tradition in survey research, but others, such as window/tab switching, are only rarely used in survey research. In this talk, I focus on the usefulness and usability of JavaScript "OnBlur" functions informing about how often and for how long respondents switch away from web surveys. For this purpose, I present the results of two empirical studies: the first study explores the impact of on-device multitasking, such as switching away to check social media notifications, on response behavior. The second study, in contrast, focuses on the consequences of looking up answers online for measuring political knowledge. The talk ends with a discussion of further fields of application for JavaScript "OnBlur" functions in survey research.