How to play Sudoku: the rules and your first solve

Updated November 1, 2026

Sudoku is a number puzzle played on a 9 by 9 grid. You never add or multiply anything: the numbers are just nine different symbols, and the whole game is working out which one belongs in each empty square. If you can follow a chain of "this cannot be that, so it must be this", you can solve Sudoku.

This guide covers the rules, how to read the grid, and a method for your first puzzle. When you want more power, the techniques guide picks up where this one stops.

The three rules

Every Sudoku has one goal: fill the grid so that the digits 1 to 9 appear exactly once in each of these:

• Every row (nine across, left to right).
• Every column (nine down, top to bottom).
• Every 3 by 3 box (the nine thick-outlined blocks that tile the grid).

The digits already on the grid when you start are called givens, or clues, and they never change. Everything else is yours to fill in. A good puzzle has exactly one solution. Puzzle Temple builds each puzzle by taking digits away one at a time and checking, after every removal, that only one solution is left, so you never have to guess: there is always a reason you can find.

Reading the grid

It helps to stop thinking of 81 squares and start thinking of 27 groups: 9 rows, 9 columns and 9 boxes. Each group needs the digits 1 to 9 once. Every square belongs to three of those groups at the same time, one row, one column and one box, and that is where all the solving power comes from. When you place a 7, you have used up the 7 in all three of its groups, so no other square in that row, column or box can be a 7.

Your first solve, step by step

1. Start where the grid is fullest. A group with only one empty square is the easiest thing on the board: the missing digit has to go there. In the box below, the digits 1 to 7 and 9 are already placed, so the empty square can only be an 8.

2. Pick a digit and scan for it. Choose a digit that already appears several times, say 7. Every 7 on the grid rules out its whole row, its column and its box. Look at a box that does not have a 7 yet: if only one square in it is still open for a 7, that is where it goes. This is called scanning, and it solves most of an Easy puzzle by itself.
3. Place what is forced, then look again. Every digit you place changes what is possible elsewhere. Go back to step 1 and 2 after each one; new single-square groups appear all the time.
4. When you stall, write notes. Notes let you jot the few digits a square could still be, so that a pattern shows up instead of hiding. The notes guide shows when they help and when they only add clutter.
5. Do not guess. A wrong digit is flagged straight away, and three mistakes end the game. If you cannot see the next step, look at a different digit or a different box rather than trying one to see what happens.

Choosing a difficulty

Puzzle Temple has five levels. They differ in how many digits you are given and, from Expert up, in the kind of reasoning the puzzle asks for.

Easy, Medium and Hard can all be finished with the two single-square ideas from this guide. Expert and Extreme are rated by the techniques they need, not only by the number of clues. The techniques guide explains each of them.

Playing on Puzzle Temple

• Click or tap an empty square, then a digit on the number pad, or type 1 to 9 on a keyboard. The arrow keys move between squares, and Backspace, Delete or 0 clears one.
• Notes (the N key) switch the number pad to small candidate marks. Hint (the H key) fills in one correct square, and you get three per puzzle. Undo (Ctrl or Cmd with Z) takes back moves, up to 50 of them.
• You can pause, restart, and watch the timer, and you can play as a guest with no account.
• If you create a free account and verify your email, your best times appear on the leaderboards for each level, for the week and for all time.

Start on Easy, take your time, and move up a level when finding singles starts to feel automatic.