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Sudoku Techniques

Browse Sudoku solving techniques by difficulty and family, from basic Singles to advanced Fish, Wings, and Chains.

Sudoku techniques are repeatable logical deductions that let you place a digit or eliminate candidates without an unsupported guess.

You do not need to learn the whole library at once. Follow the progression only as your puzzles require it:

Singles → intersections → subsets → Fish/Wings → Links/Chains

This page is the map of VeyraPlay's current Sudoku technique library.

Foundations

Scanning

A systematic way to search rows, columns, boxes, cells, or one digit for constrained positions.

techniques · beginnerScanning in SudokuLearn Sudoku scanning methods for rows, columns and boxes, and use simple restrictions to find missing digits and forced placements.

Crosshatching

Use existing copies of one digit in crossing rows and columns to restrict that digit inside a box.

techniques · beginnerCrosshatching in SudokuLearn crosshatching in Sudoku by using solved digits across rows and columns to eliminate positions and locate a digit inside a box.

Singles

Singles are forced placements.

Naked Single

One cell has exactly one remaining candidate.

techniques · beginnerNaked SingleLearn what a Naked Single is, why one remaining candidate forces a placement, and how to spot Naked Singles quickly in a Sudoku grid.

Hidden Single

One digit has exactly one remaining position in a row, column, or box.

techniques · beginnerHidden SingleLearn what a Hidden Single is, how it differs from a Naked Single, and how to find a digit with only one position in a unit.

Intersections

Locked Candidates

A digit is confined to the overlap between a box and a row or column.

techniques · intermediateLocked CandidatesLearn Locked Candidates in Sudoku, including Pointing and Claiming, and use box-line intersections to make logical candidate eliminations.

Pointing Pairs / Pointing Candidates

Start from a box and eliminate the digit from the rest of the shared line.

techniques · intermediatePointing PairsLearn Pointing Pairs and Pointing Candidates: when a digit is locked to one line inside a box and can be removed elsewhere on that line.

Box-Line Reduction / Claiming

Start from a row or column and eliminate the digit from the rest of the shared box.

techniques · intermediateBox-Line ReductionLearn Box-Line Reduction, also called Claiming, and use a row or column that is confined to one box to eliminate candidates inside it.

Subsets

Subsets reserve N digits for N cells in one unit.

Naked Pair

Two cells reserve two digits.

techniques · intermediateNaked PairLearn how Naked Pairs reserve two digits for two cells and eliminate those candidates from other cells in the same row, column or box.

Hidden Pair

Two digits are restricted to two cells.

techniques · intermediateHidden PairLearn how Hidden Pairs work when two digits are restricted to the same two cells, and remove the extra candidates hiding the pair.

Naked Triple

Three cells contain only three digits between them.

techniques · intermediateNaked TripleLearn the Naked Triple rule: three cells whose combined candidates contain exactly three digits, allowing eliminations elsewhere in the unit.

Hidden Triple

Three digits are restricted to three cells.

techniques · intermediateHidden TripleLearn how three digits restricted to the same three cells form a Hidden Triple and which distracting candidates can be removed.

Fish

Fish follow one candidate digit across matching rows and columns.

X-Wing

Two base sets restrict the digit to two cover sets.

techniques · advancedX-WingLearn the X-Wing Sudoku technique, how two rows and two columns form a size-2 Fish, and where the resulting candidate eliminations are valid.

Swordfish

Three base sets restrict the digit to three cover sets.

techniques · advancedSwordfishLearn how Swordfish extends X-Wing to three base and three cover units, including irregular candidate distributions and valid eliminations.

Wings

Wings use small candidate sets and peer relationships.

XY-Wing

A bivalue pivot connects two pincers and forces the shared Z candidate into one of them.

techniques · advancedXY-WingLearn the XY-Wing pattern using a bivalue pivot and two pincers, and see why the shared Z candidate can be removed from common peers.

XYZ-Wing

A three-candidate pivot changes the common-peer requirement for the Z elimination.

techniques · advancedXYZ-WingLearn XYZ-Wing with an XYZ pivot and XZ/YZ pincers, including the stricter visibility rule required for a valid Z elimination.

W-Wing

Two matching bivalue cells are connected through a Strong Link.

techniques · advancedW-WingLearn W-Wing using two matching bivalue cells connected by a Strong Link, and see why their other candidate can be eliminated from common peers.

Single-digit Strong-Link patterns

Skyscraper

Two conjugate pairs share one aligned side and force one of two roof candidates.

techniques · advancedSkyscraperLearn the Skyscraper Sudoku technique using two conjugate pairs, one aligned side and two roof candidates that force a common-peer elimination.

Two-String Kite

One row Strong Link and one column Strong Link connect through a box.

techniques · advancedTwo-String KiteLearn Two-String Kite using one row Strong Link, one column Strong Link and a connecting box to eliminate a candidate from the free endpoints.

Links, Coloring, and Chains

Strong Links

Understand false → true.

concepts · advancedStrong Links in SudokuUnderstand Strong Links, conjugate pairs and the false-implies-true inference used by W-Wings, Coloring, X-Chains and other advanced techniques.

Weak Links

Understand true → false.

concepts · advancedWeak Links in SudokuUnderstand Weak Links in Sudoku, how they differ from Strong Links, and how true-implies-false relationships power chain solving.

Sudoku Chains

Learn how alternating implications move logic across the grid.

concepts · advancedSudoku ChainsLearn how Sudoku Chains alternate Strong and Weak Links to propagate logical states, prove endpoint conclusions and eliminate candidates.

Simple Coloring

Use two states across a conjugate-pair network.

techniques · advancedSimple ColoringLearn Simple Coloring with two-color conjugate-pair networks, including the Color Trap and Color Wrap eliminations used in advanced Sudoku.

X-Chain

Follow one candidate digit through alternating links.

techniques · expertX-ChainLearn how X-Chains alternate Strong and Weak Links for one digit and eliminate candidates that see both chain endpoints.

XY-Chain

Follow candidate implications through bivalue cells.

techniques · expertXY-ChainLearn how XY-Chains connect bivalue cells, propagate candidate implications and eliminate the endpoint digit from common peers.

Uniqueness

Unique Rectangle

Avoid a local two-solution deadly pattern when the puzzle is verified to have one solution.

techniques · advancedUnique RectangleLearn Unique Rectangle Type 1, the two-solution deadly pattern it avoids, and the unique-solution assumption behind uniqueness techniques.

Recommended learning order

For a first complete path:

Scanning
↓
Naked / Hidden Singles
↓
Candidates
↓
Locked Candidates
↓
Pairs
↓
Triples
↓
X-Wing
↓
XY-Wing
↓
Strong / Weak Links
↓
short link patterns
↓
Coloring / Chains

This is a curriculum order, not a universal ranking of technique difficulty.

Technique difficulty is approximate

The same technique can be easier or harder to recognize depending on:

  • the candidate density;
  • the interface;
  • how many distracting structures are present;
  • what deductions had to happen first.

VeyraPlay difficulty labels should ultimately come from the human-style solving path rather than this library order alone.

How to use the technique library

If you are learning:

  1. read the concept;
  2. inspect a validated example;
  3. explain the elimination in your own words;
  4. practice the technique when controlled Practice exists;
  5. mix it with earlier techniques.

If you are stuck in a puzzle:

  1. identify what kind of candidate structure you see;
  2. open the relevant family;
  3. compare the proof with your board;
  4. return to Play without forcing a pattern that is not there.

FAQ

How many Sudoku techniques are there?

There is no single final count. Different solving systems name, split, or group advanced patterns differently.

Which technique should I learn first?

Learn direct placements first: scanning, Naked Singles, and Hidden Singles.

Do I need advanced techniques for Easy Sudoku?

Normally not in a well-calibrated difficulty system.

Is X-Wing harder than a Hidden Triple?

Often, but recognition difficulty depends on the board and the solver. Technique names are not a universal difficulty scale.

Explore strategy as well as technique

Knowing how a pattern works is only half the job. Sudoku Strategies explains when to change search mode and which family to inspect next.

strategies · allSudoku StrategiesBuild a practical Sudoku solving routine and learn how beginner, intermediate and advanced strategies fit around individual techniques.techniques · beginnerScanning in SudokuLearn Sudoku scanning methods for rows, columns and boxes, and use simple restrictions to find missing digits and forced placements.techniques · beginnerNaked SingleLearn what a Naked Single is, why one remaining candidate forces a placement, and how to spot Naked Singles quickly in a Sudoku grid.techniques · intermediateLocked CandidatesLearn Locked Candidates in Sudoku, including Pointing and Claiming, and use box-line intersections to make logical candidate eliminations.techniques · advancedX-WingLearn the X-Wing Sudoku technique, how two rows and two columns form a size-2 Fish, and where the resulting candidate eliminations are valid.concepts · advancedSudoku ChainsLearn how Sudoku Chains alternate Strong and Weak Links to propagate logical states, prove endpoint conclusions and eliminate candidates.