Sudoku Techniques
Learn how to play Sudoku with solving techniques that matter.
The Spicy Sudoku App teaches you these techniques in context with helpful
Method Hints that expose the next available method without spoilers.
Explore Every Sudoku Technique with Real Sudoku Examples
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Basics
Last Remaining Unit
Easy
All the cells in the domain are filled except for one, forcing the last possible digit's placement.
Naked Single
Easy
A cell has only one possible candidate and must be that digit for placement in that cell.
Hidden Single
Easy
A candidate is the only one available for a domain even if other candidates are listed.
Naked Pair
Easy-Medium
Two cells in the same domain contain two candidates, which can be removed from all cells in the rest of that domain.
Hidden Pair
Medium
Two candidates in the same domain are confined to two cells, so all other candidates can be removed from those cells.
Naked Triple
Medium
Three cells in a domain share three candidates, which can be removed from all cells in the rest of that domain.
Intermediate Sudoku
Hidden Triple
Medium
Three candidates in a domain are confined to three cells, so other candidates can be removed from those cells.
Pointing Pairs
Medium-Hard
A candidate in a box is confined to one row or column, so it can be removed from that line outside the box. In the example to the left, it is the 4.
Although we have shown a column for pairs and a row for triples, either could have been either a column or a row.
Claiming Pairs
Medium-Hard
A candidate in a row or column is confined to one box, so it can be removed from the rest of that box. In the example shown to the left, it is the 4.
Although we have shown a column for pairs and a row for triples, either could have been either a column or a row.
Pointing Triple
Medium-Hard
A candidate in a box is confined to three cells on one row or column, eliminating it from that line outside the box. In this case, it is a 5.
Claiming Triple
Medium-Hard
A candidate in a row or column is confined to three cells in one box, eliminating it from the rest of that box. Also a 5 in this case.
Advanced Sudoku: Wings & Links
XY-Wing
Medium-Hard
XY-Wing is an advanced Sudoku technique using three cells with only two candidates each: one pivot and two wings. All other cells that can see both wings will have a shared-candidate elimination.
XYZ-Wing
Hard
XYZ-Wing is an advanced Sudoku technique using one pivot with three candidates and two wings with two candidates each. All other cells that can see the pivot and both wings will have a shared-candidate elimination.
Skyscraper
Hard
Skyscraper is an advanced Sudoku technique using one candidate that appears in exactly two cells in each of two rows or columns. When one side lines up, all other cells that can see both opposite ends will have that candidate elimination.
W-Wing
Hard
W-Wing is an advanced Sudoku technique using two matching cells with the same two candidates, connected by a candidate that has only two possible positions in a row, column, or box. All other cells that can see both matching cells will have an elimination of the other shared candidate.
Two-String Kite
Hard
Two-String Kite is an advanced Sudoku technique using one candidate linked through a row, a column, and a box. When the links form a kite shape, all other cells that can see both loose ends will have that candidate elimination.
Turbot Fish
Hard
Turbot Fish is the most effective advanced Sudoku technique. If you learn just one Sudoku technique beyond pointing/claiming, it should be this one.
Turbot Fish uses one candidate linked through two strong pairs. All other cells that can see both loose ends will have an elimination of that candidate.
Advanced Sudoku: Fish Patterns
X-Wing
Hard
X-Wing is an advanced Sudoku fish technique using one candidate that appears in exactly two cells in each of two rows or columns. When those four cells form a rectangle, that candidate can be eliminated from the rest of the matching columns or rows.
Finned X-Wing
Hard-Extreme
Finned X-Wing is an advanced Sudoku fish technique that almost forms an X-Wing, except for one extra candidate called a fin. If the fin is true, or if the X-Wing is true, certain cells that see both possibilities can still have that candidate eliminated.
Sashimi X-Wing
Hard-Extreme
Sashimi X-Wing is an advanced Sudoku fish technique where the X-Wing pattern is almost present, but one corner is missing and replaced by extra candidates called fins. The eliminations come from cells that would be eliminated by the X-Wing and can also see the fin cells.
Swordfish
Hard-Extreme
Swordfish is an advanced Sudoku fish technique using one candidate that appears in two or three cells across each of three rows or columns. When those candidates are confined to the same three columns or rows, that candidate can be eliminated from the rest of those columns or rows.
Finned Swordfish
Extreme
Finned Swordfish is an advanced Sudoku fish technique that almost forms a Swordfish, except for one or more extra candidates called fins. If the fins are true, or if the Swordfish is true, certain cells that see both possibilities can still have that candidate eliminated.
Sashimi Swordfish
Extreme
Sashimi Swordfish is an advanced Sudoku fish technique where the Swordfish pattern is almost present, but part of the fish is missing and replaced by extra candidates called fins. The eliminations come from cells that would be eliminated by the Swordfish and can also see the fin cells.
Jellyfish
Extreme
Jellyfish is an advanced Sudoku fish technique using one candidate that appears in two, three, or four cells across each of four rows or columns. When those candidates are confined to the same four columns or rows, that candidate can be eliminated from the rest of those columns or rows.
Extreme Sudoku: The Hardest Techniques
Simple Coloring
Hard-Extreme
Simple Coloring is an advanced Sudoku technique using one candidate and two color groups linked by strong pairs. If one color creates a contradiction, the other color must be true. Cells that see both colors can also have that candidate eliminated.
Unique Rectangle
Hard-Extreme
Unique Rectangle is an advanced Sudoku technique that looks for a deadly pattern: four cells that could create a puzzle with two solutions. Since a valid Sudoku has only one solution, extra candidates in the rectangle can often be eliminated.
Alternating Inference Chain
Extreme
Alternating Inference Chain is an advanced Sudoku technique that follows a chain of strong and weak links between candidates. If the chain forces a contradiction, or if both ends see the same candidate, the puzzle can reveal eliminations far away from where the chain began.
Guess and Backtrack
Extreme
Guess and Backtrack is what it sounds like. When logic techniques can no longer reveal a clear move, a candidate is tried and the consequences are followed until a contradiction is discovered. In that case, all interim placements are removed and a different candidate is placed. Although it is not conceptually difficult, we list it as extreme as it is difficult to keep track of.
Practice These Techniques in our App
The Spicy Sudoku App includes carefully curated puzzles across ten difficulty levels. From beginner to advanced, all of these techniques appear naturally depending on the difficulty level you are playing.
