Sudoku Techniques and Strategies | Complete Guide
Sudoku is a game of pure logic, and every puzzle — from a gentle Easy grid to the most punishing Evil challenge — can be solved without guessing if you know the right techniques. This page is your complete reference to every Sudoku solving method, organized from beginner to expert. Each technique includes a step-by-step guide, worked examples, and practice puzzles so you can master it before moving on.
New to Sudoku? Start with naked singles and hidden singles — these two techniques alone will carry you through all Easy puzzles. For a structured path through every level, see our Technique Progression Guide or the Start Here Learning Path.
Whether you’re a beginner or an expert, mastering a variety of Sudoku techniques will help you solve puzzles of any difficulty. Below you’ll find a comprehensive list of strategies, each with a brief explanation and a link to a detailed guide.
If you want to practice these techniques, check out our practice section which let’s you solve Sudoku puzzles with specific techniques.
Basic Techniques
Naked Single
Use when a cell has only one possible candidate. This is the most fundamental and frequently used technique in all puzzles.Hidden Single
Use when a candidate appears only once in a row, column, or box, even if the cell has other candidates.
Intermediate Techniques
Naked Pair
Use when two cells in a unit contain only the same two candidates. Eliminate those candidates from other cells in the unit.Hidden Pair
Use when two candidates appear only in the same two cells within a unit, even if those cells have other candidates.Naked Triple
Use when three cells in a unit contain only the same three candidates (in any combination). Remove those candidates from other cells in the unit.Hidden Triple
Use when three candidates appear only in the same three cells within a unit, even if those cells have other candidates.Naked Quad Use when four cells in a unit contain only the same four candidates. Eliminate those candidates from other cells in the unit.
Hidden Quad Use when four candidates appear only in the same four cells within a unit, even if those cells have other candidates.
Pointing Pair / Pointing Triple Use when a candidate is confined to one row or column within a box. Eliminate that candidate from the same row or column outside the box.
Box-Line Reduction Use when a candidate is restricted to a single row or column within a box, allowing you to eliminate it from the rest of that row or column.
Advanced Techniques
X-Wing
Use when a candidate appears exactly twice in two different rows and the columns match. Eliminates that candidate from other cells in those columns.Swordfish
An extension of X-Wing involving three rows and columns. Use when a candidate appears in three rows and the columns align.Jellyfish
A further extension involving four rows and columns. Use for very advanced puzzles with complex candidate patterns.XY-Wing
Use when three cells form a pivot and two pincers, allowing you to eliminate a candidate from other cells that see both pincers.XYZ-Wing
A more advanced version of XY-Wing involving three cells with overlapping candidates, allowing for further eliminations.W-Wing
Use when two bivalue cells with the same candidates are connected by a strong link on one digit.Skyscraper
Pattern-based elimination involving two strong links in different rows or columns that share one column.Two-String Kite
A pattern that allows candidate elimination based on the interaction of a row strong link and column strong link via a shared box.Empty Rectangle
Eliminate candidates by analyzing empty rectangles in boxes and their interactions with strong links.Unique Rectangle
Use the puzzle’s uniqueness property to avoid deadly patterns and eliminate candidates.Finned X-Wing
Variations of X-Wing with extra candidates (“fins”) that allow further eliminations in the fin’s box.Coloring
Use chains of candidates to find contradictions and eliminate possibilities through single-digit analysis.Chains (AIC)
Follow alternating inference chains to deduce eliminations or placements across multiple digits.BUG (Bivalue Universal Grave)
Recognize and resolve situations where only bivalue cells remain, using the uniqueness principle.ALS (Almost Locked Sets)
Advanced technique involving sets of candidates in overlapping cells that share restricted common candidates.
When to Use Each Technique
Every Sudoku puzzle has a logical solution path, and the key is applying the simplest technique that works at each step. Here is a quick reference for when each category becomes necessary:
| Level | Puzzles | Key Techniques |
|---|---|---|
| Beginner | Easy | Naked Single, Hidden Single |
| Intermediate | Medium | Naked Pair, Hidden Pair, Pointing Pair, Box-Line Reduction |
| Advanced | Hard | X-Wing, Swordfish, Coloring, Skyscraper |
| Expert | Expert–Evil | XY-Wing, Chains, ALS, Unique Rectangle |
- Always start with basic techniques. Scan the entire grid for naked and hidden singles before attempting anything more complex.
- Move to intermediate techniques when basic scanning stalls. Pairs and pointing are the breakthrough methods for Medium puzzles.
- Deploy advanced techniques only after intermediate methods are exhausted. Fish patterns (X-Wing, Swordfish) and coloring handle Hard puzzles.
- Reserve expert techniques for Expert and Evil difficulty. Chains, ALS, and unique rectangles are powerful but time-consuming to find.
Explore each technique above to learn how and when to apply it. For a complete roadmap of what to learn and when, see our Sudoku Technique Progression guide. Want to jump straight into practice? Visit our Practice Section to solve puzzles that isolate specific techniques.