Sudoku Variants
A Sudoku variant changes one or two rules of the standard 9x9 puzzle. The grid can grow or shrink, the digits can become colours, or an extra constraint can forbid two equal digits from touching. Everything else stays the same: every row, every column and every box holds each symbol exactly once.
Each page below states the rules first, then shows how the usual techniques change — because a variant that only renames the digits plays exactly like the original.
Variants by grid size
4x4 Sudoku
Four digits in a 4x4 grid with 2x2 boxes. The usual starting point for children.
6x6 Sudoku
Digits 1-6 with 2x3 boxes. More room than 4x4, far less work than 9x9.
16x16 Sudoku
A 16x16 grid with 4x4 boxes, using 1-16 or hexadecimal symbols A-F.
Smaller grids remove candidates faster, so they teach the same logic with less arithmetic. Larger grids keep the rules intact and add bookkeeping instead.
Variants that add a rule
Killer Sudoku
Cages carry a sum in the corner, and a digit cannot repeat inside its cage.
Sumoku
Every completed row and column must add up to one shared target number.
Colour Sudoku
Nine colours replace the digits. Each row, column and box shows all nine once.
Anti-King Sudoku
The same digit may not sit a chess king’s move apart, diagonals included.
Minesweeper Sudoku
Clue cells count the mines around them; the rest is ordinary Sudoku logic.
Which one should you try first?
If you are still learning the standard grid, start with 4x4 or 6x6 — the rules are identical and the puzzle ends sooner. If you want arithmetic without a new grid, Killer Sudoku is the most widely published, and Sumoku is the stricter version of the same idea. If you have already finished hard 9x9 puzzles and want a new constraint rather than a bigger board, try Anti-King or Minesweeper.
Every variant on this page still falls to logic alone. The technique list covers the patterns that carry over, and the article index has the full rules for each one.