Strategy
Samurai Sudoku Strategy & Tips
A practical strategy guide for Samurai Sudoku: start in the shared boxes, scan by digit, hunt hidden singles, keep tidy notes, and work outward from the centre grid.
Play Samurai SudokuThe core idea
Let the overlaps do the work
A Samurai puzzle is five sudokus that talk to each other. Almost every strong habit comes down to two ideas: find the cells that are constrained twice, and keep passing what you learn across the shared boxes. Solving five grids one after another leaves most of the puzzle’s information on the table.
Strategy
Eight habits that speed up a solve
01
Start in the shared boxes
The four shaded 3×3 boxes belong to two grids each, so every digit there is constrained by two sets of rows, columns, and boxes. They get pinned down first, and each one you solve feeds two grids at once.
02
Scan one digit across the whole shape
Pick a digit, say 5, and mark every place it already appears in all five grids. In each grid, the rows, columns, and boxes that already hold a 5 rule out cells. Repeat for 6, then 7. Digit-by-digit scanning finds forced moves that cell-by-cell staring misses.
03
Look for hidden singles
A hidden single is a digit that fits in only one cell of a row, column, or box, even if that cell also has other candidates. Medium puzzles depend on them. Ask “where can the 8 go in this box?” rather than “what can go in this cell?”.
04
Use notes where it pays
Do not note every cell. Add pencil marks to cells with two or three candidates, and to the rows or boxes where a digit has only two places left. The board removes notes automatically when you place a digit, so they stay trustworthy.
05
Work outward from the centre
The centre grid touches all four corners through its shared boxes. Finishing it, or even most of it, hands every corner grid a full 3×3 box of new clues.
06
Switch grids when one stalls
If a corner grid stops giving you moves, do not grind. Go to a neighbour: a digit placed there may land in a shared box and reopen the grid you left.
07
Trust red, but investigate
A red cell means a repeated digit in a row, column, or box. Both clashing cells turn red, so one of them is wrong. Undo to the last move you were confident in instead of patching digits one by one.
08
Zoom for placing, zoom out for planning
On a phone, zoom in to enter digits and notes accurately, then zoom back out to see which grid deserves your attention next. The board scrolls to follow the selected cell.
Pitfalls
Mistakes that cost the most time
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.
By difficulty
How the approach shifts
The habits above apply everywhere. What changes is how much of the work is obvious — see the difficulty section of the guide.
On Easy
You can finish by repeating one question: which cell has only one candidate? Practise the digit scan here until it is automatic — it is the same skill Medium and Hard demand at scale.
On Medium
Naked singles run out, and hidden singles carry the rest. Add notes to the boxes where a digit has just two possible cells, and watch for the second placement to fall out of the first.
On Hard
Long stretches with no obvious move are normal. Keep notes on every cell in the region you are working, look for pairs of cells sharing the same two candidates, and remember that a solution is always reachable by logic.