Autosave — Your current game is saved in your browser after every move. If you leave the page, you'll be able to resume exactly where you left off. Saves are kept for 7 days.
Settings ⚙️ — For advanced players, the gear at the top of the page turns on the ✏️ Auto button: it fills in the candidates of every cell at once, keeping only the digits that fit a combination of their cage. The “cleaned” option goes further (locked candidates, combinations recomputed) and counts as help: the game won’t count as “No hints”. You’ll also find large text there, for easier reading.
Killer Sudoku stats — They are kept separate from your classic 9×9 sudoku and Sudoku X stats. They’re stored locally in your browser and never sent to a server.
Killer Sudoku: the sudoku of sums
Killer Sudoku blends sudoku with mental arithmetic. The 9×9 grid starts empty: instead of starting numbers, it is split into cages outlined with dotted lines. The small number in the corner of each cage gives the sum of the digits it contains.
The classic sudoku rules still apply, and each cage adds two pieces of information: a sum to reach, and a ban on repeating a digit. A two-cell cage worth 3 must hold 1 and 2; a two-cell cage worth 17, 8 and 9. That is where everything starts.
Sudoku-Land offers 3 levels (easy, medium, hard), a combination helper below the grid, notes mode, hints, autosave, a dark theme and the ⚙️ Settings menu. Every puzzle has a single solution and can be solved by logic alone, without ever guessing: each one has been checked individually.
Killer Sudoku rules
- Like a classic sudoku — every row, every column and every 3×3 box contains the numbers 1 to 9, once each.
- Cages and their sums — the digits of a cage add up to the number written in its corner.
- No repeats in a cage — the same digit never appears twice in a cage, even when it spans two boxes.
- No starting numbers — everything follows from the sums. When you select a cell, its cage lights up along with its row, column and box.
Tips for solving a Killer Sudoku
- Spot the cages with a single combination — 3 and 4 in two cells (1+2, 1+3), 16 and 17 (7+9, 8+9), 6 and 7 in three cells (1+2+3, 1+2+4), 23 and 24 (6+8+9, 7+8+9). The line below the grid gives them at a glance.
- Use the rule of 45 — a row, a column or a box always adds up to 45. Add up the cages lying entirely inside it: the difference gives the sum of the remaining cells. It also works on two or three rows at once (90, 135).
- Look for the cells that stick out — when a cage sticks out of a box by a single cell, the rule of 45 often gives that cell’s digit straight away.
- Pencil in candidates — with the ✏️ Auto button of the ⚙️ menu, every cell gets the digits that fit the combinations of its cage.
All the grids on Sudoku-Land
Frequently asked questions
What is Killer Sudoku?
It is a 9×9 sudoku that starts with no numbers at all. The grid is split into cages, outlined with dotted lines, and the small number in the corner of each cage gives the sum of its digits. A digit cannot repeat within a cage, and the usual row, column and box rules still apply.
Do you need to be good at math to play Killer Sudoku?
No: simple additions are enough. The useful combinations come up again and again (two cells adding up to 3 must be 1 and 2), and Sudoku-Land shows every possible combination of the selected cage below the grid.
What is the rule of 45?
The digits 1 to 9 add up to 45, so every row, column and box is worth 45. If the cages lying entirely inside a box add up to 38, the remaining cells of that box add up to 7. It is the main Killer Sudoku tool, and you will need it from the medium level on.
Does the Hint button work like in classic sudoku?
Yes: the Hint button opens a step-by-step solver that explains each Killer deduction (cage combinations, required digits, rule of 45…) on a small grid with the cages drawn in. Reading the steps is free; only “Apply this move” uses up a hint.