Sudoku Rules: How to Play

A phone, tablet or computer with a browser. Each player uses their own device.

You can play alone, against bots, or with friends. Everyone in the room races the same puzzle.

A Sudoku grid has 81 cells in 9 rows and 9 columns. Thicker lines split it into 9 boxes of 3 by 3 cells.

Some cells start filled in. These are the givens, and you cannot change them. Your job is to fill every empty cell.

• Every row holds the numbers 1 to 9, each exactly once.
• Every column holds the numbers 1 to 9, each exactly once.
• Every 3 by 3 box holds the numbers 1 to 9, each exactly once.

Pick an empty cell and look at its row, its column and its box. Any number already in one of those three cannot go in the cell. When only one number is left, that is the answer.

You can also work the other way. Pick a number and a box, and ask where in that box the number can still go. When only one cell is left, place it.

Each number you place rules out more options for the cells around it, so the puzzle gets easier as you go. You never need to guess.

There are four levels: easy, medium, hard and expert. The harder the level, the fewer givens you start with.

• Easy: 41 givens, 40 cells to fill.
• Medium: 31 givens, 50 cells to fill.
• Hard: 21 givens, 60 cells to fill.
• Expert: 11 givens, 70 cells to fill.

1. Host a room and share the room code, or play on your own.
2. Add bots in the lobby if you want them.
3. Start the game. Everyone moves to the game screen.
4. The host picks the level with the minus and plus buttons at the top. The level is remembered on the host’s device for next time.
5. The race starts once everyone has reached the game screen. Anyone still reading the instructions is waited for. Anyone else slow to arrive gets about 10 seconds before the race starts without them.

1. Everyone gets the same puzzle at the same moment, and your clock starts.
2. Tap an empty cell, then tap a number on the pad below the grid.
3. If the number is right, it goes in. If it is wrong, it flashes red, stays out of the grid, and counts as a miss.
4. Keep going until every cell is filled. Your time locks in the moment you place the last number.
5. Once you finish, you see the standings so far while you wait for the others.
6. The race ends when everyone still in it has finished. Then the host can start a new puzzle.

A strip along the top shows every player in the race. Each one has a small view of their grid, showing which cells they have filled, and how far along they are as a percentage.

You see their progress, never their numbers. When someone finishes, their percentage turns into their time.

The fastest correct finish wins. Everyone who finished is ranked by time, fastest first.

Anyone who has not finished is ranked below every finisher, by how much of the grid they have filled.

Misses are only a count on your own board and do not change your place by themselves. A wrong number never goes in, but it costs you a wait of 3, 5 or 10 seconds, whichever the host picked before the race: the screen blurs behind a countdown and you cannot play until it ends, so your clock keeps running while you wait.

Times are kept to a fraction of a second, so two players rarely tie even when their times look the same on screen.

Your board also shows a score. You earn points for every correct number, more on harder levels, plus bonuses along the way.

Bonuses come for finishing a row, a column or a box (one move can finish all three), for filling a cell that had several numbers it could still be, and for speed: the sooner you place a number after your last correct one, the bigger the bonus. Paused time does not count against it.

The score is just for fun. It does not decide who wins. Time does.

Every wrong number counts as one miss and makes you wait. Before each race the host picks how long: 3, 5 or 10 seconds. The counter on your board shows how many you have. It stays green while you have none and turns red at 3.

There is no limit. Misses keep counting up, and you can still win.

Select a cell and tap the pencil to turn on notes for it. The cell then shows the small numbers it could still be, given what is already in its row, column and box.

Notes update by themselves as you fill the grid. Tap the pencil again to turn them off for that cell.

Select a cell and tap the light bulb for a hint. The hint walks you through that one cell, step by step, and highlights the part of the grid each step talks about.

• First it tells you which numbers the cell’s row is missing.
• Then which numbers its column is missing, and which numbers its box is missing.
• Then it crosses out the numbers the column and box rule out, until it is left with the numbers the cell could be.
• If only one number is left, the last step places it for you. If more than one is left, the last step turns on notes for the cell.

Hints are open to everyone, as often as you like. They do not add time or count as misses, but reading them takes time, and the clock keeps running.

Any player can pause the race for everyone, and any player can resume it. While it is paused, every board is hidden so nobody can plan ahead.

Paused time does not count. Every clock picks up where it left off.

• Ties: finishers are ranked by exact time, so a true tie is very rare.
• Someone leaves: they drop out of the race and the standings. The race ends when everyone still in it has finished.
• Someone never finishes: the race keeps going. The host can start a new puzzle for everyone at any time with the reset button next to the level.
• A late joiner: if you arrive more than a few seconds after the race starts, you wait and join the next one. You will see a message that the race is in progress.
• Time running out: there is no time limit. The clock only measures how long you took.
• A closed tab when playing solo: your unfinished puzzle is saved on your device. Come back at the same level and you pick up the same puzzle, with your numbers, misses and time.
• A closed tab in a group: a new race always deals a fresh puzzle for everyone.
• New puzzle: the host can deal a fresh puzzle at any time with the reset button. Every player gets it at once.

The host can add up to three bots in the lobby, each set to easy, medium or hard. Bots race the same puzzle as everyone else and show up in the strip like any player.

A bot fills one cell at a time, starting with the cells that have the fewest options, the way a person would. Now and then it tries a wrong number and takes a miss.

An easy bot takes several seconds per cell and loses to a steady player. A hard bot fills a cell every couple of seconds and is a real race.

Host a room on your own and start. You get a puzzle at the level you picked and race your own clock.

Your best time for each level is kept on your device. When you finish you see it, or a note that you just set a new personal best.

Host a room and send the room code or invite link. Friends open it on their own phones, wherever they are, and join the same race.

Open joinme.games/watch on a TV or laptop and enter the room code. The big screen shows every player’s grid and progress side by side, so the room can watch the race.

Everyone plays on their own phone. The TV only watches.

• Tap a cell to select it. Cells with the same number light up together.
• Tap a number on the pad to place it. The small number under each pad button shows how many of that number are still to place.
• On a keyboard, press 1 to 9 to place a number in the selected cell.
• The pencil turns notes on and off for the selected cell.
• The light bulb gives a hint for the selected cell. Use the arrows to step through it.
• The pause button, or P or Escape on a keyboard, pauses the race for everyone.
• The sun and moon button switches between a light and a dark board.
• The host has the level and new puzzle buttons at the top.

How do you play Sudoku?

Fill every empty cell of the 9 by 9 grid so that each row, each column and each 3 by 3 box holds the numbers 1 to 9 exactly once. On Join Me Games, tap a cell, then tap a number. A wrong number does not go in and counts as a miss.

How many players can play Sudoku here?

One or more. Play alone, add up to three bots, or invite as many friends as you like. Everyone races the same puzzle.

Can you play Sudoku alone?

Yes. Host a room on your own and start. Your best time for each level is kept on your device, and an unfinished puzzle is saved if you close the tab.

How do you win a Sudoku race?

Finish the grid fastest. Finishers are ranked by time. Players who have not finished come after them, ranked by how much of the grid they filled. Misses and score do not change the ranking.

What happens if I make three mistakes?

Nothing. The miss counter turns red at 3, but there is no limit. You keep playing and can still win.

Do hints or notes count against you?

No. Hints and notes are free to use as often as you like. The only cost is the time you spend on them, since the clock keeps running.