How to play sudoku

Sudoku is a classic number puzzle for one player. The board is a grid of nine rows and nine columns, cut into nine boxes of three by three squares. Some squares already hold a digit, and your job is to fill in all the others. Tap an empty square, then tap a digit on the number pad under the board. When every square is filled correctly, the puzzle is solved.

Sudoku rules in short

Every row, every column and every three by three box must contain the digits 1 to 9, each exactly once. Those are the whole rules, and they are the same in an easy sudoku and in a hard one. There is no adding up and no maths: the digits are just nine different symbols, and the puzzle is about working out where each one can go. The small boards follow the same rules with fewer digits: a 4x4 sudoku uses the digits 1 to 4 in boxes of two by two squares, and a 6x6 sudoku uses the digits 1 to 6.

Every puzzle here has exactly one solution, so there is always a reason for the next digit. Tap a digit you have already placed and every copy of it lights up on the board, which makes it easy to see which rows, columns and boxes already have it.

Sudoku for beginners: how to get started

If you have never played, begin with the Micro level: a tiny four by four board with the digits 1 to 4, a sudoku for kids and for first steps. The rules are the same, but there is very little to keep in your head. Then try Mini, a six by six board with the digits 1 to 6, and when that feels easy, move to Easy on the big nine by nine board. The very first Easy puzzle even shows you which square to try first.

A good way to start any puzzle is to pick a digit and ask where it can still go. Look at one box, check which of its rows and columns already have that digit, and see whether only one square is left. Then move on to the next digit. Rows, columns and boxes that are almost full are the easiest to finish, so look for those first.

Easy, medium, hard, expert and evil sudoku

The game has seven levels on three board sizes: a tiny 4x4, a mini 6x6 and the classic 9x9, and you can switch between them whenever you like. The level is not a guess based on how many digits are given: every puzzle is graded by the tricks a person needs to solve it.

Micro sudoku, 4x4

A four by four board with the digits 1 to 4, split into four boxes of two by two squares. A 4x4 sudoku is always an easy sudoku: it is quick, it needs only the simplest moves and it is a friendly first step for kids or for anyone who has never played. It is also a nice way to see how the rules work before you meet the nine digits.

Mini sudoku, 6x6

A six by six board with the digits 1 to 6, split into boxes of two rows and three columns. It is quick and gentle, a step up from 4 by 4 and a good way to learn the tricks, or something to play when you have only a minute.

Easy sudoku, 9x9

A full nine by nine board that needs only the simplest moves: a square where just one digit fits, or a digit that has just one place left in its row, column or box. It is a simple sudoku for beginners and for a relaxed few minutes.

Medium sudoku

A few clever moves appear, such as digits that point along a line and pairs of squares that share the same two digits. You will want to use notes here.

Hard sudoku

A hard sudoku needs real patterns. This is where it pays to write notes in the squares and to learn the named tricks below. If you like a challenge, hard is the level where sudoku starts to feel difficult in a good way.

Expert sudoku

Tough patterns such as X-Wing and XY-Wing are needed, and a puzzle can take a good while. If a pattern is new to you, Hint explains it step by step.

Evil sudoku

The hardest puzzles of all, an extreme sudoku for people who like a real fight. Logic alone may not finish an evil sudoku: sometimes you have to test a digit, follow it through and see whether it leads to a clash.

A cute, aesthetic sudoku game

This is sudoku with an aesthetic of its own: a clean white board in a deep teal frame, soft mint-green colors, rounded number keys and gentle chimes when a row, a column or a box is complete. As you collect gems, new backdrops open up, from Peach Fizz and Blueberry Milk to Lavender Haze and a dark Midnight Garden, so the game can look the way you like it. It is meant to feel like a cozy little break, not a test.

Notes, auto notes and hints that teach

Notes, also called pencil marks, are small digits you write in a square to remember which digits could still go there. Turn Notes on and tap digits to write or remove them. Auto notes fills in all the possible digits for you in one tap, and when you place a digit, the matching notes in its row, column and box are cleared automatically.

When you are stuck, press Hint. The first press points at the part of the board to look at. The second explains the trick that works there, shows the squares involved and lets you place the digit, so each hint is a small lesson rather than just an answer. There is no answer sheet and no solve button, because the fun is in finding the move yourself. If you have made a mistake, Hint finds it first. A puzzle solved with no hints and few mistakes earns three gems.

Sudoku tips and strategies

The best sudoku tip is to look at one digit at a time. Pick a digit, say 5, and go through the boxes: in each one, check which squares are already blocked by a 5 in the same row or column and see where it can still go. Digits that already appear many times are the easiest to finish, so start with those. Then do the same with the rows, columns and boxes that are the fullest, because a unit that is missing only two or three digits gives up its answers quickly.

After every digit you place, look again: each new digit blocks squares in its row, column and box and often opens a new move. When the obvious moves run out, turn on Notes, or use Auto notes, and look for squares with only one note left or digits that fit in only one place. Never guess. Every puzzle has just one solution, and a wrong guess can sit unnoticed for a long time. If you are tired, take a break, because a fresh look often finds the move at once.

Sudoku tricks and techniques: how to solve sudoku

Every sudoku, from easy to expert, can be solved with a handful of named techniques. Here are the ones you will meet, from the simplest to the trickiest. The game names each of them when a hint uses it, so it is also a gentle way to learn how to solve sudoku, even hard sudoku puzzles.

Naked single and hidden single

A naked single is a square where every digit but one is already ruled out by its row, column and box, so the last one has to go there. A hidden single is a digit that has only one possible square left in a row, column or box, even though that square may still allow other digits. These two moves solve most easy puzzles.

Pointing and claiming digits

When, inside a box, a digit can only go in squares that all lie in one row, that digit cannot go anywhere else in that row. That is pointing. Claiming is the same idea turned round: when a digit in a row can only go in squares that all lie in one box, it cannot go anywhere else in that box.

Pairs, triples and quads

If two squares in the same row, column or box can only hold the same two digits, those digits belong to those two squares, so you can strike them from every other square in that group. This is a naked pair. A hidden pair is the mirror image: two digits that fit in only the same two squares, which means those squares can hold nothing else. Triples and quads work the same way with more squares.

X-Wing, Swordfish and wings

An X-Wing appears when a digit can go in just two squares in each of two rows, and those squares sit in the same two columns. The digit has to fill one diagonal pair or the other, so it cannot go anywhere else in those two columns. Swordfish stretches the idea to three rows, and tricks such as XY-Wing, Skyscraper and W-Wing link a few squares together to rule out a digit. They are the tools of the hard and expert levels.

Daily sudoku, streaks and gems

Every day there is a new daily sudoku, the same for everyone that day. It gets harder through the week: easy at the start of the week, medium in the middle, hard on Friday, expert on Saturday and a real evil puzzle on Sunday. Solve it each day to grow your streak.

For every puzzle you earn up to three gems, and the gems you collect open new backdrops for the game: Mint Leaf, Peach Fizz, Blueberry Milk, Lavender Haze and a dark Midnight Garden. The game also keeps your best time at each level.

Play sudoku online on your phone or computer

This free sudoku game opens right on this page, with nothing to download and no account to make. On a phone you tap the squares and the number pad. On a computer you can click, or use the keyboard: the digits 1 to 9 to fill a square, the arrow keys to move, N for notes, H for a hint and U to undo. There is no time limit, you can pause the clock by tapping it, and your game is saved automatically, so you can leave in the middle of a puzzle and come back to it later.

Questions

Is sudoku free to play here?

Yes. It is a free sudoku game: there is nothing to download and you do not need an account. Your gems, best times and daily streak are saved on your device automatically.

How do you play sudoku?

Tap an empty square, then tap a digit on the number pad. Every row, every column and every box has to end up with each digit once, and the digits that are already on the board show you where to start. On a computer you can also type the digits and move with the arrow keys.

What are the rules of sudoku?

Fill the grid so that every row, every column and every three by three box contains the digits 1 to 9 exactly once. A digit may not repeat inside a row, a column or a box. There is no adding up and no maths, only logic, and the rules are the same in an easy sudoku and a hard one: only the puzzle changes.

Is there an easy sudoku for beginners?

Yes. Start with Micro, a tiny 4 by 4 board with the digits 1 to 4, then try Mini, a 6 by 6 board, or go straight to Easy, where only the simplest moves are needed. The first Easy puzzle shows you where to begin, and Hint explains each trick in plain words.

Is there a hard or extreme sudoku?

Yes. Medium adds a few clever moves, Hard needs real patterns, Expert needs tough ones such as X-Wing and XY-Wing, and Evil is the hardest of all, an extreme sudoku where you may have to test a digit to see where it leads.

What is the difference between easy, medium, hard, expert and evil sudoku?

The level tells you which tricks a puzzle needs, not how many digits it starts with. Easy needs only the simplest moves, medium adds digits that point along a line and pairs, hard needs patterns, expert needs tough patterns and evil goes beyond them.

Which sudoku sizes are there: 4x4, 6x6 or 9x9?

All three. Micro is a 4 by 4 sudoku with the digits 1 to 4 and boxes of two by two squares. Mini is a 6 by 6 sudoku with the digits 1 to 6, whose boxes are two squares tall and three wide. The classic 9 by 9 board comes in five levels, from Easy to Evil.

How do you play 4x4 sudoku?

Fill the 4 by 4 grid so that every row, every column and every two by two box has the digits 1 to 4 exactly once. It is the same as the big game with fewer digits, so it is a good first sudoku for kids and for anyone who has never played. Tap a square, tap a digit, and use Hint if you get stuck.

Is there a medium or hard 4x4 sudoku?

Not on the 4 by 4 board. It is small, so every 4x4 puzzle is an easy sudoku, and that is what makes it a gentle place to start. For more of a challenge move up to Mini 6x6, or to Medium, Hard, Expert and Evil on the 9 by 9 board.

Is there a daily sudoku?

Yes. A new daily sudoku appears every day, the same for everyone that day, and it gets harder through the week, from easy at the start to a real evil one on Sunday. Solve it each day to grow your streak.

Is it a sudoku for kids or for adults?

For both. Kids can start with the 4x4 Micro board, where only the digits 1 to 4 are used, then try the Mini board and the first easy puzzles, where nothing runs out and a hint explains every move. Adults can use it as a calm few minutes and climb to the hard, expert and evil levels for a real challenge.

Can I write notes in the squares?

Yes. Turn on Notes and tap digits to write small pencil marks in a square. Auto notes fills in every digit that could still go there, and when you place a digit the matching notes in its row, column and box are cleared for you.

What if I am stuck? Can I see the answer?

Press Hint. The first press points at the part of the board to look at and the second explains the trick and shows the digit for the next square, so you learn something each time. There is no answer sheet and no solve button, because the fun is in finding it. Hints cost gems: a puzzle with no hints and few mistakes earns three gems, a couple of hints still earn two, and more earn one.

Does every puzzle have only one solution, and do I have to guess?

Every puzzle has exactly one solution. Easy, medium, hard and expert puzzles can be solved by logic alone, so there is never a reason to guess. Evil puzzles may ask you to test a digit and see whether it leads to a clash.

Will the game tell me when I make a mistake?

Yes. With Mark mistakes on, a wrong digit turns red at once, and Hint will point out a slip before anything else. You can turn this off in the settings if you would rather find your own mistakes.

Can I undo a move?

Yes. Undo takes back your last moves, one at a time, and Erase clears a square. On a computer, Ctrl+Z and Ctrl+Y undo and redo.

Is there a time limit?

No. A clock runs while you play so you can beat your best time, but nothing runs out. Tap the clock to pause, and it also stops when you open a menu or leave the page.

Can I print sudoku puzzles or get a sudoku pdf?

Not at the moment. This is a game made to be played on screen: you write notes, ask for hints and collect gems, so there are no printable sheets, no pdf and no sudoku book to download.

Is there samurai sudoku, killer sudoku or a bigger board?

Not yet. The game is classic sudoku on the 9 by 9 board plus the smaller Mini 6 by 6 and Micro 4 by 4 boards. Variants such as samurai, killer, word or math sudoku and bigger boards such as 16 by 16 are not here.

Is there a sudoku app?

There is nothing to install. The game opens in your browser, works on a phone much like an app would, and keeps your progress on your device, so you can close the page and continue later.

Is this a cute, aesthetic sudoku?

That is the idea. The board is clean and soft, in mint green with a deep teal frame, and the gems you collect unlock calm backdrops such as Peach Fizz, Lavender Haze and a dark Midnight Garden. It is made to feel like a cozy break, not a test.

Is sudoku a good brain game?

It is a gentle one. You look for where each digit can go, rule out the rest and plan a few steps ahead, which many people enjoy as a calm mental workout with no pressure.

Does it work on a phone?

Yes. It works on phones, tablets and computers. On a phone you tap the squares and the number pad, and you can leave at any time and continue later.