People are generally poor reporters of time spent using digital technology. Advancing smartphone features, such as the iOS Screen Time application, allow researchers to obtain more objective measurements of digital technology use. Truth and Bias models were used to test how self-reported social networking site use aligns with device-reported use as recorded by the iOS Screen Time app (N = 1585). This study explored use across four major platforms (Facebook, Instagram, Twitter, Snapchat) and examined how individual differences moderate biases in reports. Participants overestimated their use for all platforms at comparable levels. Moderation by individual differences was not consistent. These findings add to the growing call from researchers to utilize assessments other than self-reports in measuring digital technology use.