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Sudoku Rules and Strategies

Sudoku is a logic puzzle with simple rules. Whether you are solving your first grid or refining your technique, these rules and strategies will help you progress.

Technique groups

Every Sudoku can be solved by pure logic. Browse the technique groups below — from the basics through advanced forcing chains — to learn the strategies Sudoked.com uses in its hints.

Highlighted Sudoku row and box narrowing the choices to one number

Basics

The essential Sudoku rules and foundational solving techniques every player should know before moving on to advanced strategies.

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Sudoku grid with a blue number tile being placed into the final cell

Singles and direct techniques

The simplest logical placements: a single candidate or a single cell for a digit, plus direct elimination techniques that immediately reveal a placement.

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Four matching Sudoku candidates connected in a fish pattern

Intersections, subsets and fish

Elimination techniques based on locked candidates, naked and hidden subsets, and basic fish patterns (X-Wing, Swordfish).

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Three Sudoku candidate pairs joined in a wing pattern

Strong links and three-cell wings

Patterns built on conjugate pairs (strong links) and three-cell wing structures that use bivalue cells to force eliminations.

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Four candidate cells forming a unique rectangle with one extra candidate

Uniqueness techniques

Eliminations that exploit the guarantee of a unique solution by identifying deadly patterns (Unique Rectangles and Unique Loops) and removing the candidates that would create them.

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An advanced network of linked Sudoku candidate pairs

Advanced sets, fish, wings and strong links

Larger subsets (quads), bigger fish (Jellyfish), four-cell almost-locked-set wings and rings, and grouped three-link strong-link chains.

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A large wing of bivalue Sudoku cells with one exceptional extra candidate

BUG and larger ALS wings

Bivalue Universal Grave patterns and five-to-seven-cell almost-locked-set wings and rings.

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An alternating Sudoku candidate cycle leading to an elimination

Cycles and forcing chains

Closed forcing-chain loops (cycles) and open forcing chains of increasing complexity, from simple single-value chains through dynamic and nested reasoning.

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A detailed reference to 64 Sudoku solving techniques

Sudoked.com documents 64 named Sudoku solving techniques and variants in a structured reference designed for both developing players and experienced solvers. The collection begins with the fundamental rules, notes, singles and direct placements, then progresses through intersections, naked and hidden subsets, fish patterns, strong links and three-cell wings. It continues into specialist methods including Unique Rectangles, Unique Loops, BUG patterns, almost-locked-set wings and rings, grouped strong-link structures, bidirectional cycles and forcing chains. Organizing these Sudoku strategies by logical family makes it easier to understand how one method develops into another and to choose the right subject to study next.

Every technique has its own guide built around a real Sudoku position. Step-by-step explanations describe how to recognize the pattern, which rows, columns, boxes, cells and candidates are involved, and why a placement or candidate elimination follows logically. Annotated screenshots show the important candidates, links and affected cells directly on the grid, allowing the written reasoning to be checked visually. These are also the techniques used by Sudoked's logical hint system: during a game, the solver searches for a valid next strategy, identifies the relevant pattern and explains the deduction instead of merely revealing a digit. Together, the articles provide a practical route from learning how to solve Sudoku to studying advanced candidate logic in depth.

Play sudoku without ads on Sudoked.com

Every page on Sudoked.com is sudoku no ads — the rules page, the game, statistics and level cards. No trackers, no promoted content, no interruptions. Just the puzzle and the logic.