Play Sudoku Online Free — No Download

How to Play

1. Choose a level: Easy, Medium, Hard or Expert. The clock starts as soon as the grid appears.
2. Tap an empty square to select it. Its row, column and 3×3 box light up so you can scan them quickly.
3. Tap a number on the pad (or type 1 to 9) to write it in. Tap the same number again, or press Erase, to clear it.
4. Switch on Notes to jot small pencil marks for the digits a square might hold.
5. Fill every square correctly to finish. Your time is your score, so faster is better.

Rules

Every row, every column and every one of the nine 3×3 boxes must contain the digits 1 to 9 exactly once. The dark digits at the start are clues and cannot be changed. Each puzzle is built by the computer and checked with a solver, so it always has one and only one correct answer. A second checker solves it the way a person would to rate it: Easy to Hard never need guessing, while Expert needs tricks beyond pairs, such as chains of linked squares.

If you place a digit that repeats inside a row, column or box, both clashing digits turn red with a wavy underline. The game does not tell you when a digit is merely wrong, so careful thinking still matters. You get three free hints per puzzle; each one fills in a correct digit, picking your selected square when it needs fixing. Every hint adds 30 seconds to your final time, and the result screen tells you how many you used.

Tips & Strategy

• Hunt for hidden singles. Pick a digit, then check one box at a time. If only one square in that box can take the digit, it must go there — even when that square has other options.
• Use the highlight to count. Tap a placed digit and every copy of it glows. Their rows and columns show where that digit cannot go.
• Look for naked pairs. If two squares in a row can only be 4 or 7, those two digits are taken. Remove 4 and 7 from the notes of every other square in that row.
• Note the tight spots only. Mark squares with two or three options; placed digits clean up the notes for you.
• Work on the busiest area first. Rows, columns and boxes holding six or seven digits break open fastest.

Game Modes

There are four levels, rated by the solving techniques a puzzle needs rather than by the number of clues alone. Easy leaves around 40 clues, and every step is a single: a square with only one possible digit, or a digit with only one possible square in a row, column or box. Medium needs only singles too, but with about 32 clues they are harder to spot, so notes help. Hard always needs at least one step beyond singles, such as a naked pair or a digit that points along one line of a box. Expert needs even deeper reasoning than that and usually leaves the mid-twenties of clues.

The Daily Challenge is a Medium puzzle that is the same for everyone on a given day. Solve it to keep your streak alive, then share your time and level with a spoiler-free result line.

Play with Friends

This is a solo puzzle, but the daily grid makes a lovely race: everyone gets the same puzzle, so compare finishing times with friends or family. Tap Share to post your time on WhatsApp or Telegram without giving away a single digit.