SEGUI (SEGUL GUI) is an ultrafast, memory efficient, cross-platform tool for phylogenomic data manipulation and summary statistics calculation. We develop SEGUL to address the need for a high-performance and accessible phylogenomic tool. It is particularly well-suited for large-scale phylogenomic projects, especially those involving thousands of loci and hundreds of samples. Additionally, SEGUL is capable of handling small Sanger sequences effectively.