With the rise of Web-based applications, it is both important and feasible for human-computer interaction practitioners to measure a product’s user experience. While quantifying user attitudes at a small scale has been heavily studied, in this industry case study, we detail best Happiness Tracking Surveys (HaTS) for collecting attitudinal data at a large scale directly in the product and over time. This method was developed at Google to track attitudes and open-ended feedback over time, and to characterize products’ user bases. This case study of HaTS goes beyond the design of the questionnaire to also suggest best practices for appropriate sampling, invitation techniques, and its data analysis. HaTS has been deployed successfully across dozens of Google’s products to measure progress towards product goals and to inform product decisions; its sensitivity to product changes has been demonstrated widely. We are confident that teams in other organizations will be able to embrace HaTS as well, and, if necessary, adapt it for their unique needs.