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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.

Core Sudoku strategies

Every Sudoku can be solved by pure logic. Here are the basic 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 construction

Intersections, subsets and fish

Locked candidates, naked and hidden subsets, and fish described through their objects, base sectors and cover sectors.

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Three Sudoku candidate pairs joined in a wing construction

Strong links and three-cell wings

Alternating inference chains (AICs) built from strong-link nodes and weak inferences, plus small ALS constructions such as XY-Wing and XYZ-Wing.

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Four candidate cells forming a unique rectangle with one extra candidate

Uniqueness techniques

Conditional eliminations that use an explicitly stated unique-solution assumption to avoid swappable Unique Rectangle and Unique Loop configurations.

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An advanced network of linked Sudoku candidate pairs

Advanced sets, fish, wings and strong links

Larger locked sets, larger basic fish, ALS-XZ wings and rings, and longer or grouped alternating inference chains.

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

BUG and larger ALS wings

BUG uniqueness deductions and five-to-seven-cell ALS-XZ wings and double-linked rings. These are separate logical families collected at a similar study level.

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An alternating Sudoku candidate cycle leading to an elimination

Cycles and forcing chains

Open AICs, continuous rings, contradiction chains, and exhaustive forcing deductions, with every assumption kept explicit.

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A detailed reference to 64 Sudoku solving techniques

Sudoked.com organizes its English technique guides around the modern mathematical families: locked and almost locked sets, fish, and alternating inference chains (AICs). Uniqueness and exhaustive forcing deductions state their additional assumptions separately. Familiar historical names remain as searchable aliases, while each guide defines the actual cells, candidate sets, sectors, links, and visibility conditions that make the deduction valid.

Each guide uses a concrete Sudoku position and a candidate-by-candidate proof. The text identifies the operands first, then states the exact placement or elimination and why it follows. Annotated screenshots illustrate those relations but do not define them by shape. The guides document page-level technique concepts; the live hint engine and its generated explanations are maintained and tested separately.

Play sudoku without ads on Sudoked.com

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