Killer Sudoku (PuzzleMadness)

Killer Sudoku combines sudoku with sums. The grid usually starts with no digits at all; instead it is divided into cages of two or more squares, each with a total. The digits in a cage must add up to that total, and every row, column and 3x3 box still holds 1 to 9 once. PuzzleMadness advises being comfortable with hard sudokus before starting these.

The daily page opens today's puzzle on its own, and its title carries the date (on 28 October 2026 it read "Daily Medium Killer Sudoku Puzzle for Wednesday 28th October 2026"). Each day brings four separate grids. Easy, Medium and Hard each have one, and the Mixed page serves a fourth grid of its own, marked with the level it has that day. Past days stay in the archive, so a missed puzzle can be played later, and there is a print version and an image download of the grid. PuzzleMadness does not publish solutions. The site tells you when you have finished a grid correctly or made a mistake. Each completed puzzle adds to your total on the Killer Sudoku monthly and all-time leaderboards, where only your best score on any one puzzle counts.

The key fact is that every row, column and box adds up to 45. If the cages inside a box cover all but one square, that square is 45 minus their sum. Small cages with extreme totals (3 in two squares, 24 in three) have only one set of digits, and they are the next place to look.

PuzzleMadness is a British puzzle site with dozens of daily puzzle types in the browser, from many sudoku variants to logic grids such as Nurikabe, Hashi and Slitherlink. It is free to play and carries ads. A free account keeps track of the puzzles you have finished and puts your name on the leaderboards, and the badges next to usernames mark how many puzzles a player has completed.