Learn the patterns behind the challenge
If an X-wing or a pair is unfamiliar, work through the Sudoku deduction examples. To study a puzzle from its starting clues without revealing the whole answer, use the step-by-step Sudoku solver. Difficulty labels vary between publishers; this site’s Expert label describes the techniques used by its own grader.
Evil, master and extreme Sudoku levels
Evil, master and extreme are names used for difficult Sudoku, rather than separate rules. Our Expert puzzles need advanced patterns such as wings. Difficulty scales differ between collections, so these are the hardest puzzles offered here, without a claim to be the hardest ever made. For a step down, try hard Sudoku.
A strategy for expert puzzles
Do not confuse fewer givens with a harder puzzle. Difficulty comes from the logical techniques required to finish it.
What makes these puzzles expert
Each expert puzzle needs at least one advanced pattern: an X-wing, a swordfish or a Y-wing. Our solver confirmed that every one can still be finished by logic, without trial and error.
Spotting an X-wing
Pick a number with full notes. Find two rows where that number fits in exactly two cells, and both pairs sit in the same two columns. The number must occupy one of each pair, so you can remove it from every other cell in those two columns.
Extreme Sudoku without guesswork
Some puzzle collections label their toughest grids extreme, evil or master. Here, Expert is the top level, and it is defined by the techniques needed, not by an unsolvable feel. If a step seems impossible, refresh your notes and check for pairs before looking for a wing.
Use the tools at your own pace
Notes record possibilities. Undo reverses your last change, one move at a time. Fill notes lists candidates from your current entries; Redo restores an undone move. Restart replays the same starting puzzle. A hint explains a step before placing a number. Pause hides the grid and stops the timer, and your game is saved on this device so you can come back later.
Ready for another puzzle?
Choose New puzzle to start again, or visit the daily challenge for a puzzle that stays the same throughout the day. Prefer paper? Make a printable Sudoku sheet at the same level.
A few helpful answers
Yes. The game works in your browser. Progress is saved on this device when local storage is available.
Turn Notes on, select an empty cell, then choose numbers to add or remove pencil marks. Turn Notes off to enter a final number.
Yes. Every puzzle has exactly one solution, and our step-by-step solver finished each one using logical techniques before it was published.
With Auto-check on, a number that does not fit the finished grid gets a red outline and is counted as a mistake. There is no game over. Turn Auto-check off in the settings if you prefer to find errors yourself.
Yes. Use the arrow keys to move, type 1 to 9 to enter a number, press Backspace or Delete to erase, N to switch Notes on or off and U to undo.