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Killer Sudoku - Free Online Cage Puzzle

Killer Sudoku combines the logical placement of classic Sudoku with the arithmetic twist of cage-based sum constraints. Instead of the familiar 3x3 box borders, the grid is divided into irregularly shaped groups of cells called cages. Each cage displays a small target number in its corner, and the digits you place inside must add up to exactly that total. On top of that, no digit can repeat within a single cage, giving you an extra layer of deduction before you even consider the standard row and column rules.

Because cages can span across rows, columns, and even traditional box boundaries, every puzzle becomes a satisfying blend of number placement and mental arithmetic. You will find yourself reasoning about which combinations of digits can produce a given sum, then cross-referencing those possibilities against what is already placed in each row and column. It is this interplay between addition and elimination that makes Killer Sudoku so engaging.

Whether you are a seasoned Sudoku solver looking for a fresh challenge or a newcomer drawn to math-based puzzles, Killer Sudoku on Mini Puzzles offers a clean, distraction-free experience. A new puzzle is available every day, and you can play as many additional puzzles as you like in unlimited mode. No account required, no ads, and it works on any device.

How to Play Killer Sudoku

Killer Sudoku follows the same core principle as classic Sudoku: fill every row and column with the numbers 1 through 9 without repeating any digit. The twist is that the grid has no 3x3 box borders. Instead, cells are grouped into dotted-line cages, each with a target sum you must match.

Solving a Killer Sudoku puzzle requires balancing two constraints at once: the digits in every cage must add up to the cage's target, and no digit can appear more than once within a cage, row, or column. Read on for a step-by-step breakdown.

Basics

  • 1

    Understand the Grid

    The puzzle is a 9x9 grid, but instead of thick 3x3 box borders you will see dotted outlines marking irregularly shaped cages. Each cage contains 2 to 5 cells and shows a small number in the top-left corner. This number is the target sum for that cage.

    17
    8
    3
    6

    8 + 3 + 6 = 17

  • 2

    Rows and Columns: No Repeats

    Just like standard Sudoku, every row must contain each of the digits 1 through 9 exactly once, and every column must do the same. This rule applies across the entire grid regardless of cage boundaries.

    Each Row: 1-9

    1
    2
    3
    4
    5
    6
    7
    8
    9

    Each Column: 1-9

    1
    2
    3
    4
    5
    6
    7
    8
    9
  • 3

    Cage Sums Must Match

    The digits inside each cage must add up to the target number shown in the cage's corner. For example, a two-cell cage labelled "7" could contain 1+6, 2+5, or 3+4. Figuring out which combination fits is the heart of Killer Sudoku.

    7
    3
    4

    3 + 4 = 7

    15
    9
    6

    9 + 6 = 15

    10
    1
    2
    3
    4

    1 + 2 + 3 + 4 = 10

  • 4

    No Duplicate Digits in a Cage

    Even if the arithmetic works out, you cannot repeat a digit within the same cage. A cage with target sum "4" containing two cells cannot be 2+2. It must be 1+3. This rule significantly narrows the possibilities and is one of your strongest solving tools.

    Valid

    4
    1
    3

    1 + 3 = 4

    vs

    Invalid

    4
    2
    2

    No duplicates allowed

  • 5

    No 3x3 Box Borders

    Unlike standard Sudoku, the thick 3x3 box borders are removed in Killer Sudoku. The cages replace them as the primary grouping mechanism. You only need to worry about three constraints: each row has unique digits, each column has unique digits, and each cage adds up to its target with no repeated digits.

Tips & Strategies

Learn the Key Combinations

Certain cage sums have very few valid combinations. A two-cell cage with sum 3 can only be 1+2, and a two-cell cage with sum 17 can only be 8+9. Memorizing these forced combinations gives you instant placements.

Start with Small Cages

Two-cell cages have the fewest possible combinations, so they are the easiest to narrow down. Solve these first to anchor your progress, then work outward to larger cages.

Use the 45 Rule

Every row and column sums to 45 (since 1+2+...+9 = 45). If you know the sum of all but one cage in a row, subtract from 45 to find the remaining value. This is one of the most powerful Killer Sudoku techniques.

Cross-Reference Rows and Cages

When a cage spans two rows, you can combine row-level elimination with cage-sum logic. If you know three of four cells in a cage, the row constraint may reveal the last digit even before the arithmetic does.

Controls

Mouse / Trackpad

Click any empty cell to select it, then click a number (1-9) to fill it in. Click the pencil icon to toggle notes mode, and use Clear to remove a number.

Touch Screen

Tap any empty cell to select it, then tap a number to place it. Tap the pencil icon to enable notes mode for marking possible candidates in each cell.

Frequently Asked Questions

What is Killer Sudoku?

Killer Sudoku is a variant of classic Sudoku that replaces the traditional 3x3 box constraint with cage-based sum constraints. The grid is divided into irregularly shaped groups of cells called cages, each marked with a target number. You must fill every row and column with the digits 1 through 9 without repeating, and the digits inside each cage must add up to the cage's target with no duplicates. It was first published in Japan in the mid-2000s and has since become one of the most popular Sudoku variants worldwide.

How do cages work?

Each cage is a group of adjacent cells outlined with a dotted border. A small number in the top-left corner of the cage indicates the target sum. For instance, if a three-cell cage is labelled "15", the three digits you place inside must add up to exactly 15. Cages typically contain between 2 and 5 cells and can stretch across row and column boundaries, which is what makes the puzzle challenging and unique.

Can digits repeat inside a cage?

No. Every digit within a single cage must be unique, just like the rule for rows and columns. This means a two-cell cage with a target sum of 10 cannot contain 5+5; the only valid option would be combinations like 1+9, 2+8, 3+7, or 4+6. The no-repeat-in-cage rule is one of your most powerful solving tools because it dramatically limits the possible digit combinations for each cage.

What strategies help with cage sums?

Several key techniques will help you crack cage sums more quickly:

  • Forced combinations: Some sums have only one possible combination. A two-cell cage of 3 must be {1,2}, and a two-cell cage of 17 must be {8,9}. Learn these and you get instant placements.
  • The 45 rule: Each row and column sums to 45. If all but one cage in a row is known, subtract from 45 to deduce the missing value.
  • Elimination: List possible digit combinations for a cage, then eliminate any that conflict with digits already placed in the same row or column.
  • Cage-row intersection: When a cage sits entirely within one row, its digits are guaranteed to be unique within that row, which limits the options for other cells in the same row.
Are there still 3x3 box rules in Killer Sudoku?

In our version of Killer Sudoku, the traditional 3x3 box borders are removed entirely. Cages serve as the replacement grouping mechanism, so you only need to satisfy three constraints: unique digits in each row, unique digits in each column, and the correct sum with no repeats in each cage. Some other implementations keep the 3x3 box rule as an additional constraint, but here on Mini Puzzles the cages are the sole group-based rule beyond rows and columns.

How difficult is Killer Sudoku compared to regular Sudoku?

Killer Sudoku is generally considered harder than standard Sudoku because no cells are pre-filled with given digits. You start with a completely empty grid and must derive every placement from cage sums and row/column logic. However, the arithmetic provides its own form of guidance: small cages with extreme sums (very low or very high) have very few valid combinations, giving you strong starting points. Once you learn the common sum combinations, many Killer Sudoku puzzles become approachable even for intermediate solvers.

Is Killer Sudoku on Mini Puzzles free?

Yes, Killer Sudoku on Mini Puzzles is completely free. There is no account required, no advertising, and no subscription. A new daily puzzle is released every day at midnight UTC, and unlimited mode lets you play as many randomly generated puzzles as you want. The game runs in any modern browser on desktop, tablet, or phone.

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