Samurai Sudoku

Samurai Sudoku joins five classic 9×9 sudoku grids into one big puzzle. Four grids sit in the corners and a fifth sits in the middle, overlapping each of them by one 3×3 box, so the sheet looks like a large X. Play Samurai Sudoku online free in your browser, with no download, on a laptop, tablet or phone. Every puzzle is generated fresh and checked to have exactly one solution.

How to play

• Normal sudoku rules in every grid: each row, column and 3×3 box of all five 9×9 grids must contain the digits 1 to 9 once.
• Shared corner boxes: the middle grid’s four corner boxes are also the inner corner boxes of the outer grids. A digit in a shared box counts for both grids, so its row and column run through two grids at once.
• Fill the sheet: select a cell, then type or tap a digit. The puzzle is solved when all 369 cells are right.
• Zoom: on a phone, the first tap on the board zooms in around that spot. Drag to pan, pinch to zoom, or use the minus, plus and Fit buttons (or the + and – keys).

Choose Easy, Medium or Hard. Easy puzzles start with about 170 given digits and Medium with about 125, and both can be finished using only naked and hidden singles. Hard puzzles start with about 95 givens and need techniques such as pointing pairs, box-line reduction and naked or hidden pairs. The Daily button opens a Medium puzzle that is the same for everyone on a given date.

Tools in the game

• Notes: switch on Notes (or press N) to pencil in candidates. When you place a digit, the game removes that digit from the notes of every cell it sees, in every grid that cell belongs to.
• Highlight: tints the selected cell’s rows, columns and box and every copy of its digit.
• Conflicts: when it’s on, a digit that repeats in a row, column or box turns red.
• Hint: fills in one cell and explains why. If a digit you entered is wrong, the hint fixes that first. Otherwise it finds a naked single (only one digit fits the cell) or a hidden single (the only place for a digit in a row, column or box), preferring the cell you selected. With no single available, it just reveals a cell. Each hint adds 30 seconds.
• Check: marks any digit you entered that doesn’t match the solution.
• Undo and Redo: step back and forward through your moves, notes included.

The timer pauses with P, Esc or the Pause button, and when you switch tabs. Your unfinished puzzle, best and average times per level, solved counts and daily streak are saved in your browser; open Stats to see them.

Tips for solving Samurai Sudoku

• Start in the shared boxes. A cell in a shared corner box is limited by two rows, two columns and one box, so it often has fewer candidates than any other cell on the sheet.
• Pass information between grids. When you finish a shared box, both grids gain nine digits. Work back and forth instead of trying to complete one grid in isolation.
• Scan for hidden singles. Pick a digit and look at each box: if only one cell in the box can hold it, place it. On Easy and Medium this is enough to finish.
• Use pointing pairs on Hard. If a digit’s candidates inside a box all sit in one row, that digit can be removed from the rest of that row, even in the neighbouring grid.

FAQ

Is Samurai Sudoku free?

Yes. It’s free with no account and nothing to install.

How is Samurai Sudoku different from regular sudoku?

It uses five overlapping 9×9 grids instead of one. The rules inside each grid are the same, but the shared boxes link the grids, so a deduction in one can unlock another.

Do the puzzles have only one solution?

Yes. The game builds each puzzle by removing digits from a complete sheet and keeps only puzzles that a logic solver can finish and a search solver confirms have exactly one solution.

Can I play on a phone?

Yes. The board fits narrow screens; tap to zoom in, drag to pan and pinch to zoom out. Touching the board doesn’t scroll the page.

Can I play with a keyboard?

Yes. Arrow keys move and jump across the gaps between grids, 1 to 9 enter digits, Backspace erases, N toggles notes, Z and Y undo and redo, H gives a hint and P pauses.

Want a single grid instead? Play classic Sudoku, or try Killer Sudoku for cage sums. For more solving methods, read our guide to advanced sudoku techniques.