How to play Sudoku Variants

Classic sudoku — every row, column and box holds each digit once — plus one extra rule that depends on the variant. Also known as Sudoku X, Windoku, Jigsaw (Irregular), Kropki, XV, Anti-Knight, Anti-King, Non-Consecutive, Even–Odd, Thermo, Sandwich, Arrow, Little Killer, Consecutive Lines, Whisper Lines.

▶ Play Sudoku Variants ⊞ Open the solver

The rules

All variants: each row, column and box (or jigsaw piece) contains every digit exactly once.
Sudoku X: both main diagonals also contain every digit once. Windoku: the four shaded 3×3 windows do too.
Jigsaw: the boxes are replaced by irregular pieces of the same size.
Kropki: a white dot joins digits one apart; a black dot joins digits where one is double the other; no dot means neither. XV: X joins digits adding to 10, V adding to 5; no letter means neither.
Anti-Knight / Anti-King: squares a knight’s move apart / touching squares never repeat a digit. Non-Consecutive: side-by-side squares never hold consecutive digits.
Even–Odd: grey squares are even, grey circles odd. Thermo: digits strictly increase from each thermometer’s bulb to its tip.
Sandwich: a number outside a row or column is the total of the digits between the 1 and the 9. Arrow: a circled digit equals the sum of the digits along its arrow. Little Killer: a number outside points down a diagonal and gives its total.
Consecutive Lines (purple): the digits on a line form a consecutive run in any order. Whisper Lines (green): neighbouring digits along the line differ by at least 5 (3 in a 6×6).

Playing Sudoku Variants on Puzzle Solvers

Pick a variant, a size and a difficulty, then press New Puzzle. The extra rule is shown under the grid.
Tap a square, then a digit on the number pad (or type it). Or tap a digit first and then the squares you want it in.
Switch to Notes (N) to pencil in candidates; hold Shift while typing for a quick note.
Clashes turn red as you go. Hint explains the next digit, including any variant reasoning that leads to it.

Open the Sudoku Variants game →

Using the Sudoku Variants solver

Choose the variant and size, then enter the givens and the variant clues (or press Sample).
Press Solve and step through: pencil marks, singles, the variant’s own rule, pointing digits, pairs and triples — with candidates shown.

Open the solver →

A worked example

Kropki 6×6: a black dot joins R1C1 and R1C2, so they are 1–2, 2–4 or 3–6 in some order. A white dot joins R1C2 and R1C3, so R1C2 has a neighbour one apart.

If R1C2 were 6, R1C3 would be 5 — but the square under R1C3 is also joined by a black dot, which 5 can’t make in a 6×6. So R1C2 isn’t 6, and the candidates shrink from there.

Strategies

Use the extra groups. In X and Windoku the diagonals and windows are full groups — look for hidden singles in them just like in boxes.
Pencil marks first. Variants make candidate lists shrink fast. Write them in, then apply the variant rule to each pair of squares.
Dots and gaps. In Kropki, a black dot can only be 1–2, 2–4, 3–6 or 4–8. A missing dot rules out both kinds — just as strong a clue.
Thermometer ends. On a thermometer of length 5 in a 9×9, the bulb is at most 5 and the tip at least 5.
Pointing. When a digit’s places in one group all see a square, that square can’t hold it — this is extra powerful with knight and king moves.

Common mistakes

Forgetting the variant rule once the grid looks like a normal sudoku.
In Kropki and XV, ignoring the meaning of a missing dot or letter.
On thermometers, allowing two equal digits — they must strictly increase.

Where it comes from

Sudoku variants grew alongside sudoku’s popularity in the 2000s: Sudoku X and Jigsaw appeared in newspapers, Kropki came from Japanese puzzle magazines, and Thermo, Anti-Knight and Non-Consecutive became favourites at the World Sudoku Championship.

Frequently asked questions

Which variant should I start with?

Even–Odd or Sudoku X — they feel most like classic sudoku. Then try Jigsaw and Kropki.

Why are there no digits in some Kropki puzzles?

Because every dot is shown, the dots and gaps alone are enough to lead to one answer.

Is there always one answer?

Yes — every puzzle here is checked to have exactly one solution.

Can I enter a variant puzzle from a book?

Yes — open the Sudoku Variants Solver, choose the variant and enter the givens and clues.

Keep going

All guides: How to play every puzzle and game.