Sudoku Strategies
Sudoku Tips for Beginners
New to Sudoku? Start with these two fundamental strategies that will help you solve easy and medium puzzles right away.
Scan for Last Digits - Look at any row, column, or 3x3 box that is almost complete. If eight of the nine numbers are already filled in, the missing digit is your answer. This is one of the simplest beginner Sudoku strategies and a great place to start every puzzle.
Find Hidden Singles - When a number can go in only one cell within a row, column, or 3x3 box, that is called a hidden single. Scan each group and ask: "Where can this number go?" If there is only one possible cell, fill it in.
These two techniques can help you solve most easy Sudoku puzzles and many medium ones. As you improve, move on to pencil marks and more advanced strategies.
Advanced Sudoku Techniques
Once you're comfortable with the basics, these strategies will help you tackle hard and evil puzzles:
Pencil Marks - Write small candidate numbers in empty cells to track which values are still possible. This is essential for every advanced technique and the key to solving harder puzzles systematically.
X-Wing - When a number can only appear in the same two columns across two different rows, you can eliminate that number from those columns in all other rows. Look for matching pairs that form a rectangle on the grid.
Swordfish - An extension of X-Wing across three rows and columns. Harder to spot, but powerful for eliminating candidates in difficult puzzles.
Master these techniques in our tutorials, or jump straight into hard Sudoku and evil Sudoku to put them into practice.