Play Dominosa online Works — plays right here, unlimited puzzles
Guide updated October 2026 · Runs via WebAssembly (native port)
Dominosa is a domino puzzle: a complete set of dominoes was laid out in a rectangle, the numbers were copied down, and the dominoes were taken away. Your job is to work out where each one was. The puzzle is named after O. S. Adler, who is credited with inventing it. The puzzle is ready below; click between two numbers to place a domino.
Controls — what does what
| Action | Keyboard | Mouse / touch |
|---|---|---|
| Place or remove a domino | Arrow keys to the gap between two numbers, Enter | Left-click between them |
| Mark two numbers as not one domino | Space | Right-click between them |
| Highlight every copy of a number | Type the number (up to two at once) | Right-click on the number |
| Undo / redo | U / R (or Ctrl+Z / Ctrl+R) | Game menu buttons |
FREE This is the complete game, free. Open source under the MIT licence: the complete puzzle, with a new grid every time.
Dominosa 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
- Cover the whole grid with dominoes, each over two neighbouring numbers.
- Every pairing in the set appears exactly once: with numbers 0–6 that is 28 dominoes, from 0-0 to 6-6.
- No two dominoes may show the same pair of numbers.
Sizes and difficulty
Presets use sets from double-3 to double-9 at Trivial and Basic, plus double-6 at Hard and Extreme. A set up to N fills an (N+2)×(N+1) grid, so the standard double-6 is 8×7. Custom can allow ambiguous puzzles with more than one answer.
Solving tips
Find the pairs that can only occur in one place on the grid: that domino must go there. Squares in corners or hemmed in by placed dominoes have only one or two possible partners. Each time you place a domino, every other spot showing the same pair is ruled out, so mark those with lines. Highlighting a number helps you count its remaining options.
Where this puzzle comes from
Dominosa 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
Is there only one solution?
Yes, by default every puzzle has a unique answer. The Ambiguous setting in Custom drops that guarantee.
How big is the grid?
It depends on the set. A set with numbers up to 6 makes an 8×7 grid of 56 numbers, covered by the 28 dominoes.
Is Dominosa free to play here?
Yes, with no limit on the number of puzzles. Dominosa 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.
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Want a game like this on your own site?
Dominosa 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.