Samurai Sudoku

This free samurai sudoku tool makes and lets you solve a samurai sudoku, the large puzzle built from five overlapping 9x9 grids, right in your web browser. There is no sign-up and nothing to install, and nothing you do is uploaded, because each puzzle is made on your own device.

Every puzzle has exactly one solution, and the built-in solver checks this before the board appears. You can play on a computer or a phone, write pencil notes for possible digits, and ask for a hint when you get stuck. Puzzles are rated easy, medium or hard, and you can print one for pencil-and-paper play.

How to use the samurai sudoku tool

1. Open the Play tab. The page shows “Generating…” for a few seconds while the puzzle is made, and you can keep working on the page while you wait.
2. Tap or click an empty cell.
3. Tap a number on the number pad, or type the digit on your keyboard.
4. To write small candidate notes instead of a digit, press the Pencil button or the P or Space key, then enter the digits you want to note.
5. Press Check to mark wrong cells in red. It also tells you how many cells are still empty.
6. Press Hint when you are stuck. It names a technique if one applies. If none does, it reveals one correct digit and says so.
7. Use Reveal cell to fill one cell, or Show solution to see the full answer.
8. Use Undo and Redo, or Ctrl/Cmd+Z and Ctrl/Cmd+Y, to step back and forward.
9. Press Pause to stop the timer, Start over to clear your entries, or New puzzle to get a fresh board.

Two play options help you avoid mistakes. Turn on “Mark repeated digits in red” to spot clashes early. Turn on “Remove pencil marks automatically” so that when you place a digit, its notes disappear from the cells it can see. On the keyboard, arrow keys move, digits enter, and Backspace erases. To continue the same puzzle on another device, press Copy link. The link opens exactly the same puzzle.

How does samurai sudoku work?

A samurai sudoku is five classic 9x9 sudoku grids: one in the centre and one at each corner. The centre grid shares one 3x3 box with each corner grid, so the four shared boxes belong to two grids at once.

Each of the five grids follows the normal sudoku rules. Every row, column and 3x3 box in a grid must hold the digits 1 to 9 exactly once. A digit placed in a shared corner box must fit both grids it belongs to, which is why the puzzle is more tightly connected than five separate grids.

Start in the shared corner boxes. Their digits are limited by two grids at once, so they often give you the clearest first moves.

How many cells does a samurai sudoku have?

A samurai sudoku has 369 cells on a 21x21 square. Five 9x9 grids would have 405 cells (5 × 81), but the four shared boxes are each counted twice. Each box has 9 cells, so 4 × 9 = 36 cells are counted twice.

Subtracting those duplicates gives 405 − 36 = 369. The corners of the 21x21 square are empty, which is why the puzzle is not a full square of filled cells.

How to play samurai sudoku?

Your goal is to fill every empty cell so that all five grids are complete and valid. Work one grid at a time when you can, checking each row, column and box for the digits it still needs. The shared boxes are the link between grids, so a digit you place there is checked against two grids.

Pencil notes help most. Write the digits that still fit in each cell, then look for two common patterns. A cell with only one possible digit is a naked single. A digit that fits in only one cell of a row, column or box is a hidden single. Both can be applied in every grid of the samurai.

Because every puzzle has exactly one solution, each correct move moves you closer to the same finished board. A wrong digit usually shows up later as a cell with no possible value, so check your work when a cell seems to have no answer.

Is samurai sudoku harder than normal sudoku?

Each of its grids follows the classic rules, so it is not harder in principle, but it is longer. The tool rates difficulty as easy, medium or hard with the same logic solver used for classic sudoku, applied to the whole puzzle. The rating depends on which techniques are needed to finish, not on the board’s size alone.

A medium samurai from the generator had 107 given digits, so a board can look crowded with clues and still need advanced steps. The size does affect how long a puzzle takes. There are 369 cells to scan, so many solvers spend more time searching a samurai board than a single 9x9 grid of the same level.

Frequently asked questions

Can I print samurai sudoku?

Yes. The Print tab prints one samurai per page, because the puzzle needs the whole page. The answers are at the end, with four small answer grids per page. You can choose Letter or A4 paper size.

Does every samurai sudoku have only one solution?

Yes. Every puzzle the site makes is checked by the built-in solver before it is shown, and it has exactly one solution. This means you can trust that a correct digit is the only correct digit.

Can I play samurai sudoku on my phone?

Yes. On a phone the board scales to the width of the screen. Use the zoom button for a closer view, and the zoomed board scrolls inside its own box.

How long does it take to make a samurai sudoku?

It usually takes a few seconds. The page shows “Generating…” while it works, and you can keep using the page during that time.

Does the timer keep running when I leave the page?

No. The timer runs while you play and stops when the browser tab is hidden or the game is paused.

Will my progress be saved if I reload the page?

Yes. Progress is saved in your browser on this device, so a reload continues the same puzzle. Progress saved on one device does not move to another, so use Copy link to open the same puzzle elsewhere.

Related tools

• Killer sudoku: Use it when you want a sudoku that adds cage totals to the classic rules.
• Jigsaw sudoku: Use it when you want irregular regions instead of square 3x3 boxes.
• 16x16 sudoku: Use it when you want a larger grid with 16 digits per row and column.
• Printable sudoku: Use it when you want a classic sudoku to print and solve on paper.
• Hard sudoku: Use it when you want a classic sudoku that needs advanced solving techniques.
• How to play sudoku: Use it when you want to learn the basic rules and techniques before trying a samurai.
• Blank sudoku grid: Use it when you want an empty grid to draw your own puzzle or test your notes.