Whether you're a complete beginner or looking to tackle Expert-level puzzles, these tips and strategies will help you improve your Sudoku skills and solve puzzles faster.
1. Scan Rows, Columns, and Boxes
The simplest technique: look at each row, column, and 3x3 box to find where a specific number can go. Start with numbers that appear most frequently on the board — they have the fewest remaining positions.
2. Use the "Last Remaining Cell" Method
If a row, column, or box has 8 of 9 cells filled, the remaining cell must contain the missing number. Always check for these easy wins first.
3. Crosshatching
Pick a number (say, 5) and look at a 3x3 box where 5 hasn't been placed yet. Check which rows and columns passing through that box already contain a 5. This often narrows down the position to just one cell.
4. Use Pencil Marks Effectively
Write small candidate numbers in empty cells. When a cell has only one candidate left, you've found your answer. Our Notes feature makes this easy — tap Notes mode and enter all possible numbers for uncertain cells.
5. Naked Pairs
If two cells in the same row, column, or box contain the exact same two candidates (and only those two), then those two numbers must go in those two cells. You can safely remove these candidates from all other cells in that group.
Example: If cells A and B in a row both contain only {3, 7}, then no other cell in that row can be 3 or 7.
6. Hidden Pairs
If two numbers can only appear in the same two cells within a row, column, or box, then those cells can only contain those two numbers. Remove all other candidates from those cells.
7. Pointing Pairs
If a candidate number within a 3x3 box is confined to a single row (or column), it can be eliminated from that row (or column) outside the box. This is one of the most useful intermediate techniques.
8. Box/Line Reduction
The reverse of pointing pairs: if a candidate in a row (or column) is confined to a single 3x3 box, eliminate it from other cells in that box.
9. X-Wing
When a candidate appears in exactly two cells in each of two rows, and these cells align in the same two columns, you can eliminate that candidate from all other cells in those two columns. This pattern forms an "X" shape on the grid.
10. Swordfish
An extension of X-Wing using three rows and three columns. If a candidate appears in two or three cells in each of three rows, and these cells are confined to three columns, eliminate the candidate from other cells in those columns.
11. XY-Wing
Find three cells where: a "pivot" cell with candidates {A, B} can see a cell with {A, C} and a cell with {B, C}. Any cell that can see both "wing" cells cannot contain C.
12. Coloring
A technique based on chains of candidate pairs. If a candidate appears exactly twice in a group, one must be true and one false. By following the chain and assigning alternating colors, contradictions can reveal which cells contain the number.
Start with the most constrained areas. Look for rows, columns, or boxes with the most filled cells. These are the easiest to solve.
Look for the most common number. If the number 8 appears seven times on the board, there are only two cells left to place it — making it much easier to solve than a number appearing only three times.
Develop a scanning routine. Experienced solvers follow a consistent pattern: scan all rows, then all columns, then all boxes. This systematic approach ensures you don't miss anything.
Recognize patterns instantly. With practice, you'll spot Naked Pairs, Pointing Pairs, and other patterns at a glance without consciously thinking through the logic.
Don't over-note. On easier puzzles, excessive pencil marks slow you down. Only note candidates in cells where you're actively working through a technique.
Easy: Can be solved using only Naked Singles — scanning each row, column, and box for the only possible number. Perfect for beginners and quick games.
Medium: Requires Hidden Singles — finding where a number can only go in one place within a group. The most popular difficulty level.
Hard: Introduces Naked Pairs, Pointing Pairs, and other elimination techniques. You'll definitely need pencil marks.
Expert: Requires advanced techniques like X-Wing and Swordfish. These puzzles test your pattern recognition and patience.
Master: Demands Coloring, XY-Wing, and chain-based reasoning. Only experienced solvers will complete these without hints.
Extreme: The ultimate challenge. May require trial-and-error combined with advanced techniques. Less than 5% of players can solve these consistently.
Guessing. Never guess. If you can't find a logical step, you're missing a technique. Use hints to learn what you're not seeing.
Forgetting to update notes. When you place a number, always remove it from the notes of related cells. Our auto-remove feature handles this automatically.
Tunnel vision. If you're stuck in one area, move to a different part of the grid. Solving cells elsewhere often unlocks the area you were stuck on.
Ignoring 3x3 boxes. Beginners often focus only on rows and columns. The 3x3 boxes are equally important and often provide the key insight.