This paper highlights the current usability issues when solving Sudoku problems. This problem is a well-known puzzle game which consists in assigning numbers in a game board, commonly of 9 x 9 size. The board of the game is composed of 9 columns, 9 rows and 9 3 x 3 sub-grids; each one containing 9 cells with distinct integers from 1 to 9. A game is completed when all cells have a value assigned, and the previous constraints are satisfied. Some instances are very difficult to solve, to tackle this issue, we have used a filtering technique named Arc Consistency 3 (AC3) from the Constraint Programming domain. This algorithm has revealed which is much related to the strategies employed by users in order to solve the Sudoku instances, but in contrast, this technique is executed in a short time, offering a good resolution guide to the users. In general, filtering techniques make easier solving Sudoku puzzles, providing good information to users for this.