The program can solve puzzles of different grid sizes: 4 x 4 (the subgrids' size is 2 x 2), 6 x 6 (the subgrids' size is 3 x 2), 8 x 8 (the subgrids' size is 4 x 2), 10 x 10 (the subgrids' size is 5 x 2), 12 x 12 (the subgrids' size is 4 x 3), 15 x 15 (the subgrids' size is 5 x 3), 16 x 16 (the subgrids' size is 4 x 4).
The formats of sudoku files: