Killer Sudoku (killersudoku.com)

killersudoku.com is one of the daily puzzle sites run by Hey, Good Game, the small studio behind Mini Sudoku, Sudoku Conquest, Hitori Conquest, Sumplete and others. Its Daily Puzzle is numbered and dated, the same for every player, and shows a difficulty label beside the date (Daily #86 on 20 October 2026 was rated Easy).

Killer sudoku keeps the classic rules: each row, column and 3x3 box holds the digits 1 to 9 once. Instead of many given digits, the grid is covered with cages drawn as dashed outlines, each with a small total in its corner. The digits in a cage must add up to that total, and no digit may repeat within a cage. Only a few digits are given at the start.

That makes the puzzle a mix of logic and arithmetic: you work out which digit combinations can make each cage's sum, then combine that with the row, column and box rules. The board has a number pad, undo and redo, an erase key, a hint and a check button, and normal, centre, corner and colour marking modes. A short tutorial with a 4x4 example shows the cage rule the first time you play.

Besides the daily there is an unlimited mode at easy, medium, hard and expert, a mini version, a cage combinations table and a strategy guide. The archive replays the past seven dailies without an account; a free account opens every daily since the first, and saves streaks and stats.

It suits sudoku players who want a daily grid with a bit of mental arithmetic, and newcomers who want the rules shown before they start.