Sudoku Variant Generator

This is the sudoku a solver reaches for once the plain one has stopped surprising them: the same grid, with one or more further rules laid over it. The usual rows, columns and boxes always apply — these are sudoku with more rules, never sudoku with different ones — and every extra rule is a setting rather than a page of its own. That means you can do the thing a book of variants cannot offer, which is switch two of them on together and find out what happens. What happens is checked rather than assumed: the finished grid is solved again under whatever rules are on, and a puzzle that turns out to have two answers is never handed over.

Grid size

How hard

The extra rules — the usual rows, columns and boxes always apply as well

Diagonal (X)

Both long diagonals also hold each digit exactly once.

Hyper (windoku)

Four extra shaded boxes also hold each digit exactly once.

Centre dots

The middle cell of every box holds a different digit from every other middle cell.

Anti-knight

No two cells a chess knight's move apart hold the same digit.

Anti-king

No two cells that touch, even at a corner, hold the same digit.

Disjoint groups

Cells in the same place within their own box — every top-left corner, every middle — hold a different digit from one another.

Non-consecutive

Cells that share a side never hold consecutive digits.

Odd and even

A shaded cell holds an even digit; a circled cell holds an odd one.

Seed (optional)

A word gives back exactly the same puzzle.

Paper size

Print size

Margin

Millimetres of blank edge, 5 to 40.

Turn the paper sideways

How to print this, or save it as a PDF

There is no PDF to download, and there does not need to be. Open the print command in your browser and choose “Save as PDF” as the destination. The page addresses and dates a browser normally prints across the top and bottom are already kept off.
Set the scale to 100%, not “fit to page”. This sheet is already the exact size of the paper you chose, so anything that resizes it makes every measurement on it wrong.
Leave the paper size in the dialog set to the same one you chose here.

Your puzzle will appear here.

What this generator does

Lays one or more extra rules over an ordinary sudoku grid, fills a grid that satisfies all of them, then removes clues only for as long as the puzzle still has exactly one answer under those same rules.

How to use this tool

Choose the grid size and how hard you want it.
Tick the extra rules. One is plenty to start with; two makes a very different puzzle.
Make the puzzle. A grid with several rules on it can take a few seconds to settle.
Show the answer, or print the puzzle with the answer on a second sheet.
Give a seed if you want the same puzzle again.

Understanding the controls

Grid size: Four, six or nine. Not every rule fits every size, and the ones that do not are simply not offered rather than offered and then refused.
How hard: Sets how few clues to aim for. Fewer than a plain sudoku of the same name, because the extra rules do some of the work a clue would otherwise have to do.
The extra rules: Tick as many as you like. Two at once is a genuinely different puzzle, and the answer is re-proved unique under whatever combination is on.
Seed: A word gives back the same grid and the same clues while the generator is unchanged, which is what you want when a room needs the same puzzle.

Common use cases

A solver who has run out of interest in the plain grid
A puzzle page where the rules have to be printed alongside
Testing whether two rules can be satisfied at once
A club or classroom set where everyone gets the same grid
Practice at a specific technique that a rule forces

Randomness and fairness

The filled grid and the order clues are removed in are decided using the browser's secure generator. Typing a seed switches to a repeatable sequence so the same puzzle can be printed twice; that path exists for reproducibility and is not cryptographically strong.

For how randomness is produced across the whole site, see how Generate Random works.

Limitations and good to know

Some pairs of rules cannot be met together, and that is proved by trying every placement: diagonal with anti-knight on a four grid, and on a six grid any two of diagonal, anti-knight, anti-king and non-consecutive. On a nine grid nothing is proved impossible, but hyper with non-consecutive has never built here, and diagonal with non-consecutive is given up on about two seeds in five. The page says which happened — no grid can exist, or none was found in the time allowed — rather than producing a puzzle that does not work.
A grid with several rules on it takes a few seconds to settle, and a pairing the search gives up on takes about five seconds to give up. That is the cost of proving the answer rather than assuming it.
The clue counts are targets, not promises. Carving stops the moment the next clue removed would give the grid a second answer, so a puzzle sometimes keeps more clues than the setting asked for.
Difficulty here is the clue count and the rules, not a measurement of which solving techniques are needed. The plain sudoku page grades by technique; this one does not claim to.