How to Play Sudoku
Master Sudoku from basics to advanced techniques - Learn strategies that expert solvers use
Solving Strategies: Beginner to Expert
Master these techniques in order to progress from basic solving to tackling expert-level puzzles.
1. Scanning (Cross-Hatching)
Look for obvious numbers by systematically scanning rows, columns, and boxes. This is your foundation technique.
Row 4 contains 1-8. The missing digit must be 9, so place it in the highlighted cell.
2. Naked Singles
After marking candidates with notes, a cell is a 'naked single' when only one candidate remains possible.
Cell contains only candidate 7 after eliminations. Commit 7 there.
3. Hidden Singles
A number is 'hidden' when it can only go in one cell within a row, column, or box, even if that cell has other candidates.
If a box needs a 7 and only one cell can accommodate it, place 7 there even if other numbers are noted.
4. Pointing Pairs/Triples
When a candidate appears only 2-3 times in a box and they're aligned in the same row or column, eliminate that candidate from the rest of that row/column.
If 5 can only be in two cells of a box and they're in the same row, remove 5 from all other cells in that row.
5. Box-Line Reduction
When a candidate in a row or column is confined to a single box, eliminate that candidate from other cells in the box.
If all the 3s in a row are in the same box, no other cells in that box can be 3.
6. Naked Pairs & Triples
When 2-3 cells in a unit contain exactly the same 2-3 candidates, those numbers must go in those cells. Eliminate them from all other cells in that unit.
If two cells in a column can only be {2,5}, no other cell in that column can be 2 or 5.
7. Hidden Pairs & Triples
When 2-3 numbers appear as candidates in only 2-3 cells of a unit, those cells must contain those numbers. Remove all other candidates from those cells.
If 4 and 9 only appear in two cells of a row, those cells can only be 4 or 9. Remove other candidates.
8. X-Wing
If a candidate appears exactly twice in two different rows, and these positions align in the same two columns (forming a rectangle), eliminate that candidate from other cells in those columns.
If 7 appears in columns 2&5 of rows 3&7 only, remove all other 7s from columns 2 and 5.
9. XY-Wing
A chain of three cells with paired candidates that allows you to eliminate a specific candidate from cells that 'see' both ends of the chain.
Find a pivot cell with candidates {X,Y} connected to cells with {X,Z} and {Y,Z}. Eliminate Z from cells seeing both wings.
10. Swordfish
Extension of X-Wing to three rows/columns. When a candidate appears 2-3 times in three rows and aligns in three columns, elimination is possible.
Like X-Wing but with 3x3 pattern. Very rare but powerful when it appears.
11. Forcing Chains
Follow a chain of implications from assuming a candidate is true or false. If both possibilities lead to the same conclusion, that conclusion must be true.
If assuming cell A=5 and A≠5 both force cell B=3, then B must be 3 regardless.
12. Advanced Pattern Recognition
Combine multiple techniques simultaneously. Look for jellyfish patterns, unique rectangles, and complex chains across the grid.
Expert puzzles often require stacking 3-4 techniques. Use our hints to learn these patterns in context!
💡 Learning Path
Start with techniques 1-3 and practice until they become second nature. Then progress through intermediate strategies (4-6), which solve most puzzles. Advanced and expert techniques (7-12) are needed only for the hardest puzzles.
Pro tip: Use our specific hints when stuck to see which technique applies. This is the fastest way to learn advanced patterns!