Sudoku looks like a numbers game, but it isn't really about arithmetic at all — you never add, subtract or do any math. It's a pure logic puzzle. Every Sudoku has exactly one solution, and that solution can always be reached through reasoning alone, never guessing. The whole skill of Sudoku is learning to see the logic that's already sitting in the grid in front of you.
This guide pulls together everything we've written about solving Sudoku into one place, ordered the way you should actually learn it: the foundations first, then the intermediate patterns that crack medium puzzles, and finally the advanced techniques that defeat the hardest grids. Work through it in order if you're new, or jump straight to the technique you're stuck on. Every section below links to a full article that walks through that idea step by step.
The Rules, in One Paragraph
A standard Sudoku is a 9×9 grid divided into nine 3×3 boxes. Some cells are already filled in — these are your "givens." Your job is to fill every empty cell so that each row, each column, and each 3×3 box contains the digits 1 through 9 exactly once. That single rule — no repeats in any row, column or box — is the entire game. Everything in this guide is just a smarter way of applying it.
Start Here: The Beginner Foundations
Before any fancy patterns, you need three habits: knowing where to look first, recognising the two most basic "forced" placements, and tracking your possibilities properly. Master these and you can already solve most easy and many medium puzzles.
- Why You Should Always Start a Sudoku in the CornersThe most efficient place to begin any grid — and the logic behind it.
- Naked Singles vs. Hidden Singles: Know the DifferenceThe two most fundamental forced placements every solver must recognise.
- Pencil Marks: The Sudoku Skill Nobody Teaches BeginnersHow to track candidates so the harder techniques become possible.
- When to Guess in Sudoku (And When Never To)Why true Sudoku never requires guessing — and what to do when you're tempted.
Level Up: Intermediate Techniques
Once the basics are automatic, medium and hard puzzles start to stall you. These techniques are the bridge. They're about spotting relationships between cells — pairs, triples, and the way one box can rule out possibilities in another.
- The Box-Line Reduction Trick That Cracks Hard SudokuHow a digit confined to one line inside a box eliminates candidates elsewhere.
- Sudoku Pair Elimination: The Technique You Use Without KnowingNaked pairs and how two cells can lock out a whole region.
- The Hidden Triplet: Sudoku's Most Overlooked TechniqueSpotting three candidates hiding among extra noise in a unit.
- Colour Coding Your Sudoku Candidates: A Visual StrategyUsing colour to track chains and spot contradictions at a glance.
Expert Patterns: The Hardest Grids
These are the techniques that separate casual solvers from experts. They rely on recognising geometric patterns spread across the whole grid. They look intimidating at first, but each one is just a careful, repeatable piece of logic — and the satisfaction of landing one is what keeps people coming back to Sudoku for years.
- X-Wing Explained: The First Advanced Sudoku TechniqueThe classic rectangle pattern — the gateway to expert solving.
- Finned X-Wing: When the Pattern Has an ExceptionExtending the X-Wing to "almost" patterns with an extra candidate.
- The Swordfish Pattern: Sudoku's Most Satisfying TechniqueThe three-line cousin of the X-Wing for the toughest puzzles.
- XY-Wing: The Sudoku Technique That Feels Like MagicA three-cell chain that eliminates a candidate you'd never spot otherwise.
- Remote Pairs: The Sudoku Chain Technique for Expert PuzzlesFollowing a chain of linked pairs across the grid to force eliminations.
- The Minimum Clue Count That Changes Everything in SudokuWhy 17 is the magic number — and what it means for puzzle difficulty.
The Best Way to Practise
Reading about technique only takes you so far; Sudoku is learned by solving. The fastest way to improve is to solve regularly at a level that's just beyond comfortable — hard enough that you get stuck, easy enough that you can work your way out. When you stall, come back to the relevant guide above, learn the one technique you were missing, and apply it immediately. That loop of stuck → learn → apply is what builds real skill.
If you'd like puzzles to practise on right now, we keep a library of free printable Sudoku in easy and hard levels — print them, solve on paper, and check your answers with the built-in key.
Browse Printable Puzzles »