Sudoku Solving Techniques
Every Sudoku is solved with logic, and the logic comes in layers. This collection walks the full ladder of Sudoku solving techniques, from the singles a beginner spots in seconds to the fish, wings, colouring and forcing chains that crack the hardest grids. Each guide explains not just what a pattern looks like but how to recognise it on a real board and why the elimination it produces is always safe.
If you are just starting out, begin with naked and hidden singles, pairs and pointing pairs, then work outward to X-Wings and beyond. Every technique here works exactly the same whether the grid holds numbers or the nine glowing shapes of Shapedoku, so you can practise each one, then try it on Hard or Extreme.
88 articles in this collection
Reading Candidate Counts in Sudoku to Guide Your Next Move
Reading candidate counts sudoku players trust points to the next move; learn how cell and unit counts reveal singles, pairs, and strong links fast.
Contradiction Testing Sudoku: Disciplined Bifurcation Done Right
Contradiction testing sudoku means assuming a candidate, following it to a clash, and eliminating it. Learn to bifurcate cleanly and why logic still wins.
Almost Locked Candidates Sudoku: Intersections That Eliminate
Almost locked candidates sudoku explained: how a digit nearly confined to a box-line intersection creates powerful, reliable candidate eliminations.
When a Sudoku Technique Finds Nothing and What to Try Next
When a Sudoku technique finds nothing, there is usually a reason. Learn why an eliminating move yields no result and what to reach for next.
How to Spot an X-Wing Fast in Sudoku
Learn to spot an X-Wing fast by finding a digit locked to the same two columns in two rows, then clearing it from the rest of those two columns.
Almost Hidden Sets Sudoku: The Hidden-Set Counterpart to ALS
Almost hidden sets sudoku mirrors almost locked sets from the hidden side, giving another route to advanced eliminations. Learn what an AHS is.
Sashimi Swordfish Sudoku: The Finned Fish That Still Works
Sashimi swordfish sudoku explained: how the finned, missing-corner form of the swordfish fish pattern still delivers valid candidate eliminations.
How to Spot Pointing Pairs Fast in Sudoku
Learn to spot pointing pairs fast by seeing a candidate confined to one line inside a box, then removing it from the rest of that row or column.
Sudoku Triangulation: Pin a Shape With Two Lines
Sudoku triangulation pins a shape into one cell using lines from two other boxes. Learn this cross-hatching move and place with confidence.
Multi-Coloring Sudoku: Linking Clusters When Simple Coloring Stalls
Multi-coloring sudoku links two separate color clusters when simple coloring runs out of room, unlocking eliminations single colors miss. A clear guide.
Set Equivalence Theory Sudoku: The Logic Behind Rings and Fish
Set equivalence theory sudoku explained: the base-set and cover-set framework behind fish, rings, and many advanced Sudoku elimination patterns.
How to Spot Naked Pairs Fast in Sudoku
Learn to spot naked pairs fast by finding two cells in a unit that share the same two candidates, then clearing those values from every other cell.
Sudoku Coloring Wrap: How Traps and Wraps Force a Solution
A sudoku coloring wrap forces a whole color to be false in one stroke. Learn how color traps and color wraps each crack a grid using simple coloring.
BUG Plus One Sudoku: How One Cell Cracks the Grid
BUG plus one sudoku explained: how the single three-candidate cell in a near-deadly pattern resolves the whole grid to one safe, unique solution.
Sudoku Candidate Map: How to Read the Grid Behind the Grid
Learn how to read a Sudoku candidate map, spot constrained cells and digits, find useful patterns, and choose the next technique without guessing.
Sudoku Candidate Overload: How to Simplify a Crowded Grid
Fix Sudoku candidate overload by cleaning notes, prioritizing constrained houses, using subsets, and switching to focused scans instead of reading marks.
Sudoku Candidate Elimination: How to Remove Possibilities Safely
Master Sudoku candidate elimination with row, column, box, subset, intersection, and chain logic while avoiding unsupported pencil-mark deletions.
What Sudoku Technique to Use Next: A Practical Decision Guide
Use this guide for what Sudoku technique to use next, from singles and locked candidates to subsets, fish, wings, and chains without random hunting.
Fireworks Sudoku: Using Intersecting Strong Links
Fireworks Sudoku combines intersecting strong links to create a small set of guaranteed positions. Learn the core pattern and how it drives eliminations.
Exocet Sudoku: A Conceptual Guide to Base and Target Cells
Exocet Sudoku uses base candidates and distant target cells in very hard grids. Learn the core relationship, verification mindset, and safe deductions.
Avoidable Rectangle Sudoku: A Careful Uniqueness Technique
Avoidable Rectangle Sudoku prevents a deadly two-solution pattern after some corners are solved. Learn when the uniqueness logic is safe and valid.
Grouped X-Cycles Sudoku: Using Box Segments as Chain Nodes
Grouped X-Cycles Sudoku lets a node represent several candidates in a box segment. Learn how grouped strong links extend ordinary X-Cycles safely.
Nice Loops Sudoku: How Closed Chains Create Eliminations
Nice Loops Sudoku closes strong and weak implications into a circuit. Learn continuous and discontinuous loop logic without losing the chain.
ALS Chains in Sudoku: Linking Almost Locked Sets Step by Step
ALS chains in Sudoku connect several Almost Locked Sets with restricted common candidates. Learn how the endpoints force clean eliminations.
ALS-XY-Wing Sudoku: Three Almost Locked Sets Working Together
ALS-XY-Wing Sudoku links three Almost Locked Sets through restricted common candidates. Learn the pattern, proof, and endpoint eliminations.
Mutant Fish Sudoku: Mixed Houses in Advanced Fish Logic
Mutant Fish Sudoku mixes rows, columns, and boxes on both sides of a fish. Learn the base-cover idea, verification steps, and common mistakes.
Kraken Fish Sudoku: Combining Fish Patterns With Chains
Kraken Fish Sudoku uses chains to extend a fish beyond direct fin eliminations. Learn the core idea, branch logic, and a safe way to verify targets.
Finned Swordfish Sudoku: How to Find and Verify the Pattern
Finned Swordfish Sudoku adds a local fin to a three-line fish. Learn the base and cover sets, the two-case proof, and safe eliminations correctly.
Sashimi X-Wing Sudoku: How the Incomplete Fish Still Eliminates Candidates
Sashimi X-Wing Sudoku is a finned X-Wing with a missing corner. Learn the pattern, the conditional logic, and where eliminations stay valid.
Turbot Fish Sudoku: A Practical Guide to the Four-Candidate Chain
Turbot Fish Sudoku links two strong links with one weak link. Learn how to spot the four-candidate chain and make safe eliminations correctly.
The Best Order to Learn Sudoku Techniques, Step by Step
The best order to learn Sudoku techniques, from singles and pairs through fish and wings to chains, so each new skill rests on the last one.
How to Spot Hidden Singles Fast in Sudoku
Learn to spot hidden singles fast with simple scanning habits that reveal the one cell a digit or shape can legally occupy in a row, column, or box.
ALS-XZ Rule Sudoku: Two Almost Locked Sets, One Elimination
The ALS-XZ rule sudoku technique links two almost locked sets through a restricted common digit to force an elimination. A clear, step-by-step explainer.
Hidden Unique Rectangle Sudoku: A Subtle Uniqueness Trick
Hidden unique rectangle sudoku explained: how the hidden form of this uniqueness technique uses strong links to safely eliminate a candidate.
WXYZ-Wing in Sudoku: A Practical Guide
Learn how WXYZ-Wings use four cells and four candidates to prove a shared elimination in difficult Sudoku puzzles.
Single Digit Sudoku Techniques: Skyscraper to Turbot Fish
Single digit Sudoku techniques made clear: skyscraper, two-string kite, empty rectangle and turbot fish, how to spot each and what they eliminate.
Grouped Nodes Sudoku: Using a Cell Cluster as One Chain Link
Grouped nodes sudoku chains treat two or three cells in a box as one link; learn how grouped nodes extend chains and unlock stubborn eliminations.
Digit Forcing Chains Sudoku: Branching From a Single Digit
Digit forcing chains sudoku branches from the two spots one digit can take in a house, then keeps the conclusion both branches share. A worked guide.
Nishio Sudoku: Single-Digit What-If Testing Done Right
Nishio sudoku explained: how careful single-digit what-if testing really works, when this method is acceptable, and where its practical limits lie.
Sudoku Uniqueness Techniques: Rectangles, BUG and Caveats
Sudoku uniqueness techniques explained: unique rectangle, hidden UR, avoidable rectangle, BUG and BUG plus 1, with the caveats each one requires.
Broken Wing Sudoku: Guardians and Single-Digit Chains
Broken wing sudoku explained: how single-digit chains and a guardian cell break an illegal loop and let you eliminate candidates with confidence.
Aligned Triple Exclusion Sudoku: Three Cells, One Verdict
Aligned triple exclusion sudoku extends aligned pair exclusion to three cells; see how a shared region and almost locked sets remove candidates.
Sudoku Chain Notation: How to Read r1c1, Links, and Shorthand
Sudoku chain notation looks cryptic until you learn it. Decode r1c1 grid references, strong and weak links, and the shorthand experts use for chains.
Sudoku Chaining Techniques: A Roadmap From Colouring to AIC
Sudoku chaining techniques from simple colouring to X-chains, XY-chains, AICs and forcing chains, with a clear roadmap for building the skill.
Cell Forcing Chains Sudoku: One Cell, Every Candidate Tested
Cell forcing chains sudoku tests every candidate in a single cell to find one shared elimination they all agree on. Learn this reliable advanced tactic.
SK Loop Sudoku Explained: One Chain, Many Eliminations
SK loop sudoku explained in plain language: how this multi-cell chain around four boxes forces many eliminations at once in the hardest puzzles.
Alternating Inference Chains in Sudoku Explained
Learn how Alternating Inference Chains connect strong and weak candidate links to produce advanced Sudoku eliminations.
Extended Unique Rectangle Sudoku: The Six-Cell Deadly Pattern
The extended unique rectangle sudoku pattern spans six cells and three shapes; learn its deadly logic and the clean eliminations it hands you.
Franken Fish in Sudoku: An Advanced Fish Guide
Learn how Franken Fish mix boxes with rows or columns to extend X-Wing, Swordfish, and Jellyfish logic.
Aligned Pair Exclusion in Sudoku Explained
Learn how testing candidate combinations in two cells can rule out values that would break nearby Almost Locked Sets.
Pattern Overlay Method in Sudoku: A Practical Guide
Learn how Sudoku templates reveal candidates that can never appear, or must appear, across every valid pattern for one symbol.
Chute Scanning in Sudoku: How Bands and Stacks Reveal Placements
Use bands, stacks, and box interactions to find hidden placements that ordinary cell-by-cell scanning can miss.
X-Cycles in Sudoku: A Practical Guide
Learn how X-Cycles use alternating strong and weak links for one candidate to create safe eliminations and placements.
The Death Blossom Sudoku Technique Explained
Understand how one stem cell and several Almost Locked Sets combine to create a precise advanced Sudoku elimination.
The M-Wing Sudoku Technique Explained
Learn how two matching bivalue cells and one strong link combine to remove a candidate across the Sudoku grid.
XY-Chains in Sudoku: A Step-by-Step Guide
Learn how a chain of bivalue cells can force one endpoint candidate and remove it from cells that see both ends.
Claiming Pairs in Sudoku: Box-Line Reduction Explained
Learn how claiming pairs and triples lock a candidate inside one box and remove it from the rest of a row or column.
Naked Triples and Quads in Sudoku Explained
Learn how naked triples and quads lock candidates into a small set of cells and create clean eliminations across a Sudoku unit.
The Sue de Coq Sudoku Technique Explained
Understand the Sue de Coq pattern at a box-line intersection and learn how its candidate split creates precise eliminations.
3D Medusa Sudoku Coloring Explained
Learn how 3D Medusa links candidates across several symbols and uses two colors to find contradictions and safe eliminations.
Sudoku Wing Techniques Compared: XY, XYZ, W and M
Sudoku wing techniques compared: XY-Wing, XYZ-Wing, W-Wing and M-Wing share one idea, and here is how to tell them apart and when each one applies.
Template Deletion Sudoku: Solving a Grid One Digit at a Time
Template deletion sudoku lists every legal pattern a single digit can take, then removes the impossible ones. Learn this systematic solving method.
Gurth's Symmetrical Placement: Solving Sudoku With Symmetry
Gurth's symmetrical placement shows how a puzzle's rotational symmetry forces digits, pairs candidates, and pins the center cell in symmetric Sudoku.
Almost Locked Sets in Sudoku Explained
Understand Almost Locked Sets, how they interact through restricted common candidates, and why they power advanced eliminations.
The Finned X-Wing Sudoku Technique Explained
Learn how a near X-Wing with one extra candidate can still remove a value when the fin and target share the same box.
Bivalue Cells in Sudoku: Why Two Candidates Matter
Learn why cells with exactly two candidates are valuable, how they support wings and chains, and when they create immediate progress.
Strong and Weak Links in Sudoku Explained
Understand strong and weak candidate links, the foundation behind coloring, chains, wings, and many advanced Sudoku deductions.
Unique Rectangle Types Sudoku: Type 1 to Type 6 Explained
The main unique rectangle types sudoku solvers use, from Type 1 to Type 6, explained with clear corners and the deadly pattern behind each one.
Forcing Chains in Sudoku: A Practical Introduction
Use controlled assumptions to follow candidate consequences and find conclusions that remain true across every possible branch.
Sudoku Fish Techniques: A Roadmap From X-Wing to Jellyfish
Sudoku fish techniques explained as a learning path from X-Wing to Swordfish, Jellyfish, and finned or sashimi fish, with clear worked examples.
Bowman's Bingo Sudoku: A Structured Last-Resort Chain Method
Bowman's Bingo sudoku is a disciplined trial-and-error method for the hardest grids. Learn how to run a clean, reversible chain and when to reach for it.
Phistomefel Ring Sudoku: The Hidden Equality Expert Solvers Love
Phistomefel ring sudoku explained: what the 16-cell ring is, why the border and corner sets hold equal digits, and how expert solvers use it.
Finned Jellyfish Sudoku: How the Fin Limits Eliminations
Finned jellyfish sudoku keeps a near-miss four-line fish alive with one stray candidate, letting you make a single safe elimination inside the fin box.
The XY-Wing Technique in Sudoku Explained
The xy-wing sudoku move is a three-cell chain that clears candidates the X-Wing cannot reach. Learn the pivot, the two pincers, and how to spot one.
The X-Wing Technique in Sudoku Explained Simply
The X-Wing Sudoku technique looks advanced but the idea is simple. Learn to spot the rectangle pattern and use it to crack hard and extreme boards.
Naked Pairs and Pointing Pairs Explained
Naked pairs sudoku players learn alongside pointing pairs are two elimination moves that unlock hard boards by removing candidates without any guessing.
The Swordfish Sudoku Technique, Explained
The swordfish sudoku technique is the three row version of the X Wing. Learn to spot it with a worked example and crack the toughest Sudoku boards.
Naked Singles and Hidden Singles Explained
The naked single sudoku move and its cousin the hidden single solve most of every easy and medium board. Learn what they are and how to spot them.
The Skyscraper Technique in Sudoku
The Skyscraper Sudoku pattern clears candidates with two short conjugate pairs of one digit. Learn to see it with a clear worked example and a hunting tip.
Simple Coloring in Sudoku, Step by Step
Sudoku coloring chains a single digit through the grid with two colors, then clears any cell that sees both. Learn the method with a full worked example.
Unique Rectangles and the Deadly Pattern
The Unique Rectangle Sudoku move uses the fact that a proper puzzle has one solution to remove candidates. Learn to spot and use the deadly pattern here.
The Jellyfish Technique in Sudoku
The Jellyfish Sudoku technique is the four by four member of the fish family, after the X-Wing and Swordfish. See how it works with a clear worked example.
The XYZ-Wing Technique, Explained
The XYZ-Wing sudoku technique extends the XY-Wing with a three candidate pivot. Learn to spot it, and see exactly which cell it lets you clear.
Hidden Pairs and Triples in Sudoku, Explained
Hidden pairs and triples unlock cells that naked pairs miss. Learn to spot them with a worked example and clear crowded candidates on hard Sudoku boards.
Remote Pairs in Sudoku
The remote pairs Sudoku technique links identical bivalue cells into a chain of opposites, so any cell seeing both ends loses both candidates.
The Two-String Kite in Sudoku
The two string kite in Sudoku joins a row pair and a column pair through a shared box to clear one cell. Learn to spot the pattern and eliminate.
The Empty Rectangle Technique, Explained
The empty rectangle Sudoku move pairs a digit trapped in one box with a strong link to clear a cell at the crossing. See it worked step by step here.
The W-Wing Technique in Sudoku
The W-Wing Sudoku move links two matching pairs through a strong link to clear a shared candidate. Learn to spot this tidy pattern with a worked example.