Play Sudoku (Solo) online Works — plays right here, unlimited puzzles
Guide updated October 2026 · Runs via WebAssembly (native port)
Sudoku is the number-placement puzzle in which every row, column and block of a 9×9 grid holds each digit from 1 to 9 exactly once. This version generates a fresh grid every time, at the difficulty you pick, and includes Jigsaw, Killer and X variants. The puzzle is ready below; click a square and type a digit to start.
Controls — what does what
| Action | Keyboard | Mouse / touch |
|---|---|---|
| Select a square | Arrow keys | Left-click the square |
| Enter a digit | Type the digit | Click, then type the digit |
| Add or remove a pencil mark | Press Enter to switch to pencil mode, then type the digit | Right-click, then type the digit |
| Clear a square | Space or 0 | Click, then press Space |
| Undo / redo | U / R (or Ctrl+Z / Ctrl+R) | Game menu buttons |
| Reveal the solution | — | Game menu → Solve (Undo takes you back) |
FREE This is the complete game, free. Open source under the MIT licence: the complete puzzle, with a new grid every time.
Solo is from Simon Tatham's Portable Puzzle Collection, © Simon Tatham and contributors, used under the MIT licence. Built from source by scripts/build-puzzles.mjs.
How to play
Fill every empty square with a digit so that:
- no digit repeats in any row;
- no digit repeats in any column;
- no digit repeats in any block outlined by thick lines.
Some squares are filled in for you as clues. In X mode the two long diagonals (shaded) must also contain each digit once. In Killer mode there are no starting digits; instead, dashed cages show the total their digits must add up to, and no digit may repeat inside a cage. Larger grids run out of digits, so they use letters after 9 (a 12×12 grid uses 1–9 then a, b, c).
Sizes and difficulty
The Type menu offers 2×2 (a 4×4 grid), 2×3 (a 6×6 grid), the standard 3×3 (9×9) and larger 3×4 and 4×4 grids. Difficulty runs Trivial, Basic, Intermediate, Advanced, Extreme and Unreasonable: up to Basic there is always at least one square you can fill outright, Intermediate and above need deductions about where a digit could go, and Unreasonable may need trial and error. There are also presets for X mode, Killer mode and 9-square Jigsaw grids with irregular blocks. Hard settings can take a few seconds to generate.
Solving tips
Start with the digit that is already placed most often and check each block for the single square it can go in. When a block's options for a digit all lie in one row or column, that digit is ruled out of the rest of that row or column. Use pencil marks once single placements dry up: two squares in a unit that can only hold the same two digits (a naked pair) let you strike those digits from everywhere else in the unit. In Killer, learn the forced combinations, for example a two-square cage totalling 3 must be 1 and 2.
Where this puzzle comes from
Solo is part of Simon Tatham's Portable Puzzle Collection, a set of about forty logic puzzles written by Simon Tatham and contributors and released under the MIT licence. Every grid is generated on the spot, so the supply never runs out, and for the grid-logic puzzles the generator makes sure each has exactly one solution, reachable by reasoning rather than guessing. The version here is the collection's own code compiled to WebAssembly; the Game menu can save a puzzle to a file and load it again, and the Type menu changes the size and difficulty.
Frequently asked questions
Does every puzzle have exactly one solution?
Yes. The generator only offers grids that can be solved by logic to a single answer; at the Unreasonable level you may need to try a digit and backtrack, but the answer is still unique.
Can I type in a Sudoku from a newspaper?
Yes. Use Game → Specific to enter a puzzle description, and the built-in solver can also solve grids it did not generate itself.
Is Sudoku free to play here?
Yes, with no limit on the number of puzzles. Solo is open-source software under the MIT licence, and every grid is generated fresh when you press New game.
Does it work on a phone or tablet?
Yes. A tap works as a click and the puzzle resizes to fit the screen. Puzzles whose controls use the right mouse button are easier with a mouse.
More you can play in your browser
Related guides
- Futoshiki (Unequal)Play Futoshiki free in your browser: fill a Latin square that obeys every greater-than sig
- Calcudoku (Keen)Play Calcudoku free in your browser: fill a Latin square so each cage hits its sum, produc
- Skyscrapers (Towers)Play Skyscrapers free in your browser: place towers of every height once per row and colum
- Nonogram (Pattern)Play nonograms free in your browser: shade the grid so each row and column matches its run
Want a game like this on your own site?
Sudoku (Solo) isn't ours to give away — we host it, we didn't write it. But eleven of the games here we did write from scratch, and those are free for anyone to put on their own page: one line of HTML, no account, no permission, no attribution beyond a credit line.