Killer Sudoku: cages and totals
Killer Sudoku keeps the classic row, column and box rules and adds groups of cells called cages. A cage total tells you the sum of its digits, normally without repetition within the cage. Read the killer Sudoku rules and solving examples to see how arithmetic adds another constraint.
Jigsaw and diagonal Sudoku
Jigsaw Sudoku replaces the square boxes with irregular regions; in a standard nine-digit puzzle each outlined region still contains every digit once. Diagonal Sudoku keeps the usual boxes and also requires every digit once on each marked main diagonal. Check the marked regions or diagonals before applying a classic technique. Neither variation is playable in the classic grid on this site.
Samurai Sudoku and larger grids
Samurai Sudoku links five overlapping classic grids. A cell in an overlap belongs to both grids, so a placement must satisfy both sets of units. A 16 × 16 Sudoku is a different format: it uses sixteen symbols in each row, column and 4 × 4 box. Check the symbol key because publishers may use different letters and digits. Neither format can be entered into this site’s 9 × 9 solver.
Classic 9 × 9
Use digits 1 to 9 with 3 × 3 boxes. Play any of the four difficulty levels on this site: easy, medium, hard and expert.
Smaller grids
Our 4 × 4 grid uses digits 1 to 4 and 2 × 2 boxes. Our 6 × 6 grid uses digits 1 to 6 and boxes two rows high by three columns wide.
More Sudoku variations
Killer adds cage totals. Jigsaw changes the regions. Diagonal adds constraints on the main diagonals. Samurai combines overlapping grids. These formats are not playable on this site at launch.
Puzzles like Sudoku
If you enjoy placing numbers by logic, you may also like Kakuro, where digits in each run add up to a clue, Futoshiki, which adds greater-than signs between cells, and nonograms, which use number clues to reveal a picture. None of these are playable here; they are mentioned only as related puzzle types.
Choose by rules, not just size
A bigger grid is not automatically a better next step. Learn the constraints first, then choose a format that suits the kind of deduction you enjoy.