With mobile device penetration increasing across the world, so is the number of people using these devices to respond to web surveys. Research has shown that data quality is lower when people use mobile devices to respond to surveys that are not designed for their use. Therefore, many administrators have optimized their web surveys for mobile devices, or at least made them mobile friendly, so the questionnaires display to utilize all available screen space. While this change should make it easier to read the questions and select responses, the research thus far suggests that while optimization helps, it may not entirely eliminate device effects. The Census Bureau's National Content Test (NCT) and the American Community Survey (ACS) developed a mobile-friendly version of their web surveys in 2015 and 2016, respectively. This research aims to compare data quality indicators for the NCT and ACS, including breakoff rates, completion times, answer changes, and the percent of mobile device users that switch to a computer, before and after the adoption of a mobile-friendly instrument.In addition to assessing the impact of a mobile-friendly instrument on each of these surveys separately, there is great value in comparing the differential gains across the surveys. Both are national probability samples, but the survey length and content varies greatly. Specifically, the NCT takes approximately 10 minutes to complete, compared to 40 minutes for the ACS. Additionally, the ACS contains more complex questions and question formats than the NCT does. The surveys were designed and optimized in the same way, allowing for a direct comparison to inform whether developing mobile-friendly instruments can improve data quality across surveys or if the effectiveness can depend on the characteristics of each survey.