This is the online appendix of the paper "Why Don't We Trace? A Study on the Barriers to Software Traceability in Practice", authored by Marcela Ruiz, Jimmy Hu, and Fabiano Dalpiaz. This contains five files: Software traceability survey.pdf - a PDF version of the survey that was used in the paper to collect information about traceability practices and the challenges experienced by practitioners; Software_traceability_InterviewProtocols.pdf - the interview protocol that was used to complement the survey with more in-depth information; Survey_Demographics_Final_V2.0.xlsx - demographic information about the participants in our study; Survey_SPSS.xlsx - the raw data used for the analysis via SPSS, and the results obtained through SPSS; Survey_StackedBar_Final_V1.4.xlsx - the Excel sheet we used to generate the stacked bar charts shown in the paper.