Daily Sudoku

How to play here

1. Choose a level: Easy, Medium or Hard. Each level is its own puzzle with its own saved progress.
2. Select a cell by tapping or clicking it. Bold digits belong to the puzzle and cannot be changed.
3. Press a digit below the board, or type it. Pressing the same digit again empties the cell.
4. Switch Notes on to write small candidate digits into an empty cell. A digit that already stands in the same row, column or box cannot be a note. Placing a digit hides it in the notes of its row, column and box; erasing the digit shows those notes again, and the notes the cell had before. Erase on a cell without a digit clears its notes.
5. Fill notes (automatic notes) writes every candidate into every empty cell at once: the digits that do not yet stand in its row, column or box. It replaces the notes you wrote, also those under your digits, so a digit you erase later leaves its candidates behind. One Undo takes it back.
6. Undo takes back one change at a time. Restart empties the board and resets the time; on a solved puzzle it also removes the solved mark.
7. Hint marks a cell that logic can fill next, gives its digit and names the technique, such as a hidden single. If candidates must be removed first, it also names the techniques for that. It uses the digits on the board, not your notes. If one of your digits is wrong, it asks you to press Check first.

Check compares your digits with the solution and marks the ones that differ. Mark conflicts, which is on at the start, marks your digits that repeat a digit in their row, column or box. Both marks use an underline and a corner mark as well as colour.

When the selected cell holds a digit, the same digit is highlighted everywhere else: cells with that digit are tinted and get a bar along their foot, and in the notes the digit sits on a filled disc. This shows at a glance where the digit already stands and where your notes still allow it.

When the puzzle is solved, Share result passes one line to the share menu of your device, or copies it: the game, the level, the day or practice number and your time, never the solution, with a link to the same puzzle.

Keyboard

The board is a single stop in the tab order. Press Tab to reach it, then use the arrow keys.

Printing

The Print button below the board prints the puzzle in its start position, without your entries. Answer on page 2 is on at the start: the solution then follows on its own page. Switch it off to print the puzzle alone. Large print makes the grid as big as the page allows. The printed puzzle is the one shown, so only today’s puzzle and earlier ones can be printed.

To choose a level, a day and 1, 2 or 4 puzzles per page, use the printable Sudoku page.

• Printable Sudoku

Small screens and large text

Large cells makes every cell at least as big as a comfortable touch target. On a narrow screen the board then scrolls sideways inside its frame. The site switches this on by itself when the cells would otherwise be too small for your text size.

Move buttons adds four arrow buttons below the board. Together with the digit buttons they let you play without touching the board at all.

What the levels mean

Every puzzle is rated by a solver that works like a person: it applies the simplest technique that makes progress and notes the hardest one it needed.

The numbers of given digits describe the puzzles published so far. No level needs a guess: the solver finishes every published puzzle with the techniques of its level.

• Sudoku rules
• Sudoku solving techniques

Example: the first moves

Look for a row, column or box that is nearly full. If a row already shows 1, 2, 3, 5, 6, 7 and 9, its two empty cells need 4 and 8. If the column of one of these cells already contains a 4, that cell is 8 and the other one is 4.

On an easy puzzle a single is always available: a cell with one possible digit, or a digit with one possible place in a row, column or box. When you cannot find one, switch Notes on and write the possible digits into the cells of one box. A cell with one note, or a digit that appears in the notes of only one cell of the box, is your next move.

Common mistakes

• Guessing. Every puzzle here has a logical next step; a guess that turns out wrong costs more time than the search for that step.
• Checking only rows and columns. The 3 × 3 box is the rule that is forgotten most often.
• Trusting notes blindly. The page hides a placed digit in the notes of its row, column and box, but it does not apply techniques such as pairs for you: after Fill notes, every note is only a candidate until you rule it out. A wrong digit also hides notes that are still possible, and stops you writing them, so press Check when the notes stop making sense.
• Reading the conflict mark as the only kind of mistake. A digit can be wrong without repeating yet. Check finds those.