Access to raw data of graphs presented in original articles to calculate effect size in meta-analysis studies of single-case research is one of the challenges that researchers encounter. Researchers typically use data extraction software programs to extract raw data from the graphs in articles. In this study, we aimed to analyze the validity and reliability of the use of PlotDigitizer software program, which is a widely used in literature and alternative to other data extraction programs, on computers with different operating systems. To accomplish this task, we performed the digitization of a total of 6.846 data points on three different computers using 15 hypothetical graphs with 20 data series and 186 graphs with 242 data series from 29 published articles. In addition, using the values we digitized we recalculated the 23 effect sizes presented in the original articles for validity analysis. Based on our sampling, we calculated inter-coder and intra-coder Pearson correlation coefficients. The results showed that PlotDigitizer could be an alternative to other programs as it is free and can run on many current and outdated systems, and it is valid and reliable as it is nearly perfect. Based on the obtained results and considering the data extraction process, various recommendations are presented for the researchers that will use PlotDigitizer program for the quantitative analysis of single-case graphs