Guide
How to Play Samurai Sudoku
Samurai Sudoku is one rule on a bigger board. Fill five overlapping 9×9 grids so every row, column, and 3×3 box holds the digits 1 to 9 once — and use the shared boxes to carry your progress from grid to grid.
Play Samurai SudokuThe objective
Fill all 369 cells with the digits 1 to 9
Samurai Sudoku is a sudoku variant made of five overlapping 9×9 grids. You win when every cell holds a digit and each of the five grids is a valid sudoku: the numbers 1 to 9 appear exactly once in every row, column, and 3×3 box.
There is no timer forcing your hand and no arithmetic — just logic. Every puzzle here has exactly one solution, so a forced next move always exists. Open the board when you are ready, or print a puzzle to solve on paper.
The layout
Four corner grids, one centre grid, four shared boxes
The centre grid overlaps each corner grid in a single 3×3 box, shaded on the board. Those 36 cells belong to two grids at once, so their digits must satisfy both. Five grids of 81 cells, minus the 36 shared cells counted twice, gives 369 cells.
Step by step
Your first puzzle in four moves
- 1
Read the layout
A Samurai puzzle is five 9×9 sudoku grids arranged like the dots on a die: four in the corners and one in the centre. The centre grid overlaps each corner grid in one shared 3×3 box, so the whole puzzle has 369 cells instead of 405.
- 2
Follow the one rule
Every row, column, and 3×3 box of every grid must contain the digits 1 to 9 exactly once. That is the whole rule set — there are no sums, no cages, and no guessing required. The clues in each puzzle lead to exactly one solution.
- 3
Use the shared boxes
A digit in a shared box counts in both grids at once. That is where Samurai gets its rhythm: solve a cell in a corner grid and it can suddenly unlock cells in the centre grid, and the centre unlocks the other corners.
- 4
Fill every cell
Select a cell, enter a digit, and use pencil notes to track candidates. Conflicts glow red as you go. The puzzle is solved the moment all 369 cells are filled correctly — the timer stops and your best time is saved on your device.
Controls
Tap, click, or type
Every method fills the same cells. Pick whichever fits the device in your hand.
Everywhere
Tap or click, then a digit
Tap a cell to select it — its row, column, and box highlight, and every matching digit lights up. Then tap a number on the pad or press 1–9. Tapping the same digit again clears the cell.
Everywhere
Notes (pencil marks)
Switch Notes on to toggle small candidate digits instead of placing a value. When you place a real digit, matching notes are removed from every cell it can see, in all the grids it touches, so notes stay tidy.
Desktop
Keyboard
Arrow keys move the selection (hopping over the empty corners of the shape). 1–9 fill, Backspace erases, Shift plus a digit toggles a note, N switches Notes mode, U or Ctrl+Z undoes, H reveals a hint, and M mutes the sound.
Phones and tablets
Zoom
Five grids on a small screen means small cells. Zoom doubles the board size inside its frame and scrolls to follow your selected cell, so notes are readable while you still see the whole shape when you zoom back out.
Rules & tools
What the board checks for you
The objective
Fill all 369 cells so that each of the five 9×9 grids is a valid sudoku: the digits 1–9 appear once in every row, column, and 3×3 box. The puzzle is won the instant the last correct digit lands.
The shared boxes
The centre grid’s four corner boxes are also the inner corner boxes of the four outer grids. A cell there belongs to two grids, so its digit must satisfy the rows, columns, and boxes of both. Those 36 shared cells are the links between grids.
Clues are locked
Given digits are bold and cannot be changed. Your own entries appear in blue. If a digit repeats within a row, column, or box, both cells turn red — that is a rule conflict, not necessarily the wrong answer, so find which of the two is mistaken.
Hints and timing
A hint fills the selected cell (or a random unsolved one) with the correct digit. It is unlimited, but a solve that used hints does not set a best time. The clock pauses while the tab is hidden.
Unique solutions
Every puzzle is checked by a solver that counts solutions and rejects anything with more than one, so you never have to guess. If you are stuck, there is always a logical next step.
Difficulty
Easy, Medium, and Hard
Levels are graded by the deductions a puzzle needs, not only by how many clues it starts with. See the strategy guide for how to tackle each.
About 170 givens — obvious singles only
Easy
Every step is a cell with only one possible digit left. Puzzles are solved by scanning for “this cell can only be a 4”. It is the right place to learn how the overlaps work, and a finish in 20–40 minutes is typical.
About 130 givens — needs hidden singles
Medium
Some cells only make sense from the digit’s point of view: a 7 has just one legal spot left in a row, column, or box. Medium puzzles require spotting those hidden singles, and pencil notes start paying for themselves.
About 100 givens — the fewest clues
Hard
The generator strips the puzzle down as far as it can while keeping a single solution. Expect long stretches where notes, cross-grid reasoning, and patience matter more than speed. Plan on an hour or more.
Mistakes
Common ways a Samurai puzzle goes wrong
Guessing across the overlap
A wrong digit in a shared box poisons two grids at once. Because every puzzle here can be solved by logic, a guess is never necessary — if you cannot find a forced move, add notes instead.
Solving each grid in isolation
Treating the five grids as separate puzzles wastes the overlaps. Re-check the shared boxes every time you make progress in a neighbouring grid.
Skipping notes on Hard
Hard puzzles have long dry stretches where no cell is obvious. Notes turn “no cell is obvious” into visible pairs and triples you can reason about.
Overusing hints early
A hint fills one cell but not the understanding of why. Use it after you have scanned every digit, and treat the revealed cell as a clue to how the region works.
Tips
Quick habits that speed up every solve
- Start in the shared boxes. A digit there works for two grids at once, so those cells get constrained fastest.
- Scan for each digit across the whole shape: find every place a 5 is already placed, and see where the remaining 5s can still go.
- Look for hidden singles — a digit with only one legal cell left in a row, column, or box — before you fill notes.
- Use pencil notes for cells with two or three candidates, and let the automatic note cleanup do the tidying.
- Work outward from the centre grid: solving it opens the inner boxes of all four corner grids.
- When stuck in one grid, switch to a neighbour. Progress in an adjacent grid often feeds back through the shared box.
- If a red conflict appears, undo back to the last placement you were sure of rather than patching cells one by one.
- On a phone, use Zoom while placing digits and zoom out to see the whole shape when planning your next move.
Devices
Play on desktop, phone, or paper
Desktop browsers
Chrome, Edge, Firefox, and Safari all run the game with no plugin. Play entirely from the keyboard, or mix mouse and number pad. On a large monitor the whole 21×21 lattice is readable without zooming.
Phones and tablets
The board scales to the width of your screen with the number pad and tools directly beneath it, so the whole game sits above the fold in portrait. Use Zoom for comfortable notes on a phone; a tablet shows five grids at a natural size.
Progress on this device
Your puzzle in progress, plus best times, solves, and streaks for each difficulty, live in local browser storage. Refresh the page and you resume exactly where you were. Nothing syncs between devices.
Questions? The FAQ covers timing, hints, and saving.