Sudoku is a logic puzzle with simple rules — but mastering it takes focus and practice. Here's everything you need to know.
Sudoku is a logic puzzle played on a 9×9 grid divided into nine 3×3 boxes. The goal is straightforward: fill every empty cell with a number from 1 to 9, so that each row, each column, and each 3×3 box contains every number from 1 to 9 exactly once. No number can repeat within the same row, column, or box. No mathematics is involved — only logic and deduction. Every sudoku puzzle begins with some numbers already placed in the grid. These pre-filled numbers are called givens or clues. The more givens a puzzle has, the easier it is to solve. An easy puzzle might start with 35 to 40 numbers already placed. An expert puzzle may have as few as 17 or 18, leaving the majority of the grid for you to work out. The three rules of sudoku are simple. First: each row must contain the numbers 1 through 9, each appearing exactly once. Second: each column must contain the numbers 1 through 9, each appearing exactly once. Third: each of the nine 3×3 boxes must contain the numbers 1 through 9, each appearing exactly once. Every deduction you make follows from these three constraints. To get started, look for the easiest placements first. Find a row, column, or box that is nearly complete — if eight of the nine cells are already filled, the missing number is obvious. Work through all of these easy wins before attempting anything more complex. This approach gets more numbers on the board quickly and creates new deductions to work with. As you fill in more cells, you will start to see which numbers can possibly go in each remaining empty cell. When a cell has only one possible number given what is already in its row, column, and box, fill it in. This is the most fundamental sudoku technique and handles most easy puzzles on its own. Once you move beyond easy difficulty, you will need to think more carefully. Writing small candidate numbers in each empty cell — known as pencil marks or notes — helps you track possibilities and spot patterns that are impossible to see otherwise. From there, techniques like hidden singles, pointing pairs, and naked pairs let you eliminate candidates and make progress even when no single cell has an obvious answer. The guides in this section cover everything from the absolute basics to the rules, history, and benefits of sudoku. If you are completely new, start with the rules guide. If you have played before but want to get better, explore the strategy guides linked here and on our strategies page.
Sudoku is played on a 9×9 grid divided into nine 3×3 boxes. Some cells start filled — these are called "givens".
Each row must contain every digit from 1 to 9 exactly once. No repeats.
Each column must contain every digit from 1 to 9 exactly once. No repeats.
Each of the nine 3×3 boxes must contain every digit from 1 to 9 exactly once. No repeats.
A "naked single" is a cell where only one digit is possible. Check each empty cell against its row, column, and box to find these.
For harder puzzles, use the notes feature to mark all candidates for each cell. This lets you spot patterns without guessing.
A "hidden single" is a digit that can only go in one spot within a row, column, or box — even if that cell could hold other digits.
Every Sudoku puzzle has exactly one solution reachable by pure logic. If you find yourself guessing, back up and look again.
Every solve awards XP — more for harder difficulties. Hit 500 XP to level up. Harder puzzles earn more, so mix up the difficulty to climb faster.
Solve at least one puzzle per day and your streak grows. Skip a day and it resets to 1. The flame icon next to your avatar shows your current streak.
Add friends by email, then challenge them to race on the exact same puzzle. Winner earns a bonus on top of the solve reward. Add friends via the Add a Friend page.
Two tabs — All-Time ranks everyone by total XP, This Week resets every Monday UTC. Your row is highlighted when you're on the page.
No. A properly constructed sudoku puzzle never requires guessing. Every puzzle has exactly one solution, and that solution can always be reached through pure logical deduction. If you feel like you need to guess, it means there is a technique you have not applied yet — not that the puzzle requires it. This is one… Continue reading on Do You Have to Guess in Sudoku? How to Solve Without Guessing
Sudoku is one of the most recognised puzzle names in the world, but most people who play it daily have never thought about what the word actually means. The answer is simpler than you might expect — and the history of where the puzzle came from is more surprising. What Does Sudoku Mean in Japanese?… Continue reading on Sudoku Meaning: The Japanese Word Behind the World’s Most Popular Puzzle
Sudoku has a reputation as a brain game — something you play to keep your mind sharp. But is there anything to that reputation, or is it just good marketing? The honest answer is that regular sudoku practice does offer real cognitive benefits, particularly for concentration and logical reasoning. Here is what we know and… Continue reading on Is Sudoku Good for Your Brain?
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