Political knowledge questions often are used in social sciences web surveys to study political literacy, identify knowledge gaps and misinformation, examine political polarization, and predict political behavior. However, knowledge questions are subject to bias when respondents look up the correct answers online. Lookup behavior can confound knowledge scores and challenge the validity of substantive analyses. Previous research has used self-reports, catch questions, paradata, and web tracking to detect lookup behavior in web surveys. In this short take, we detail the implementation, potential, and challenges of each measure. We also offer recommendations on which measures to use and how to further develop them.