Sudoku looks simple: fill a 9×9 grid so each row, column, and 3×3 box contains digits 1–9. But without a systematic approach, you'll hit walls. The difference between beginners and experts isn't luck — it's technique. From the basics to advanced patterns, here's how to solve Sudoku faster and more reliably. Practice these strategies in our free Sudoku game at MiniGamePlanet.
Naked Singles
A naked single is a cell that can only be one number. Scan each empty cell: if only one digit fits (because all others are already in that row, column, or box), fill it in. This is the first technique every solver learns. Easy puzzles can often be completed using nothing but naked singles. Always scan the entire grid before moving to harder techniques — you might find several.
Hidden Singles
A hidden single is a digit that can only go in one cell within a row, column, or box — even though that cell might have other candidates. For example, if 7 appears in eight of nine cells in a row, the 7 must go in the ninth. Check each unit (row, column, box) for digits that have only one possible home. Hidden singles unlock progress when naked singles run out.
Pointing Pairs and Claiming
When a candidate appears in only one row or column within a 3×3 box, you can eliminate that candidate from the rest of that row or column outside the box. This is "pointing" — the box points the candidate out. "Claiming" works the opposite way: when a candidate in a row or column appears only within one box, remove it from the rest of that box. Both reduce possibilities and often reveal naked or hidden singles.
Naked Pairs and Triples
If two cells in the same unit share exactly the same two candidates (e.g., both can only be 3 or 7), those digits are locked to those cells. Remove 3 and 7 from all other cells in that unit. Naked triples work the same way: three cells sharing three candidates among them. These patterns help you eliminate candidates and simplify the grid.
The X-Wing
The X-wing is an intermediate technique. For a given digit, if it can only appear in two cells in two different rows, and those cells are in the same two columns (forming a rectangle), you can eliminate that digit from the rest of those columns. The same logic applies to rows and columns swapped. X-wings often break tough puzzles when simpler techniques stall.
Swordfish and Beyond
Swordfish is a larger version of X-wing: three rows (or columns) where a digit is confined to three columns (or rows). More advanced solvers use X-Y wings, simple coloring, and unique rectangles. Don't rush to learn these — master naked and hidden singles, pointing, claiming, and X-wing first. Most puzzles up to "hard" don't require advanced techniques.
Pencil Marks and Systematic Scanning
Write small candidate numbers (pencil marks) in empty cells. Update them as you eliminate possibilities. Scan by row, column, and box — don't skip units. Many solvers get stuck because they miss a hidden single or pointing elimination. A systematic scan of the whole grid after each major move prevents oversights.
Practice Makes Perfect
Start with easy puzzles and focus on speed with naked and hidden singles. Move to medium when you're comfortable. Add pointing, claiming, and naked pairs. Save X-wing for hard puzzles. The more you play, the faster you'll spot patterns. At MiniGamePlanet, you can play Sudoku online with multiple difficulty levels. For more logic puzzles, try Nonogram, Logic Grid, or Lights Out. For more strategy tips, see our best puzzle games guide.