Sudoku puzzles with 23 clues sit just six clues above the proven minimum of 17. Expect extreme-level chain logic, fish patterns, and patient pencil-mark work from the first move.
23 clues is deep extreme territory. With 58 empty cells and very little redundancy in the givens, almost every cell starts with three or more candidates. You will not solve these with crosshatching alone.
Why so few puzzles at 23 clues? Generators rarely target this exact count - most extreme puzzles are produced at 24-26 clues because going lower requires expensive uniqueness verification. Each 23-clue puzzle is essentially a small trophy.
Begin by writing complete pencil marks across the grid - skipping this step is the single fastest way to fail at this clue count. Look for naked and hidden pairs to thin out the candidates, then scan for X-Wings and Swordfish on the digits that still have many positions. When subset and fish logic stalls, switch to coloring or XY-Wing chains. Most 23-clue puzzles need at least one chain elimination before the cascade of singles begins.
For deeper coverage of the techniques you will need, see our guides on X-Wing, Swordfish, Coloring, and the full Sudoku strategies hub.
This page is part of our Sudoku by clue count cluster. The fewer clues a puzzle has, the more advanced the techniques required. The proven minimum is 17 clues - see 17-clue Sudoku for the famous case. For the matching difficulty band see Extreme Sudoku.
Generating valid Sudoku puzzles at very low clue counts is computationally expensive because each candidate puzzle must be checked for solution uniqueness. Most generators stop at 24-26 clues because the success rate drops sharply below that. Below 17 clues no valid puzzle exists at all.
Yes. Every puzzle in our 23-clue collection has a unique solution and is solvable with logical techniques alone, but those techniques include X-Wings, Swordfish, coloring, and XY-Wing chains. If you find yourself wanting to guess, that is usually a sign you have missed a chain pattern.
A 23-clue Sudoku puzzle starts with 23 digits already placed in the grid out of 81 cells, leaving 58 cells for you to fill. Lower clue counts generally mean harder puzzles because you have less starting information.
Most experienced solvers complete a 23-clue puzzle in 25-40 minutes. Beginners may take significantly longer at this clue count, especially if pencil marks are required.
In our classification, 23-clue puzzles are rated extreme. The exact difficulty also depends on which solving techniques are required - clue position matters as much as clue count.
Yes. Open any puzzle from this page and use the print function in your browser, or visit our printable collection at /printable-sudoku for printer-optimized layouts of extreme puzzles.
Ready to put your skills to the test?
Try Final Sudoku - an ad-free Sudoku experience with smart tools