Donka Puzzle Co.
Donka Puzzle Co.'s Sudoku is a free, browser-based Sudoku game with two ways to play: a Daily Challenge — one shared puzzle per day that everyone solves together, with streaks to track how many days in a row you've completed it — and an unlimited Practice mode spanning four difficulty levels, from Easy to Expert. No download, account, or sign-up is required.
Sudoku is played on a 9×9 grid divided into nine 3×3 boxes. The goal is to fill every cell so that each row, each column, and each 3×3 box contains the digits 1 through 9 exactly once, with no repeats. Every well-formed Sudoku puzzle — including every puzzle generated here — has exactly one valid solution. Select an empty cell, then enter a number using the on-screen number pad or your keyboard. Use Notes mode to pencil in candidate numbers while you narrow down possibilities, and use Hint if you get stuck. For a fuller walkthrough, see how to play Sudoku.
Eight walkthroughs, from the basic rule to the techniques Expert grids demand. Each one is worked through with grid diagrams — the patterns are far easier to recognise than to read about.
Fill the 9×9 grid so that every row, every column, and each of the nine 3×3 boxes contains the digits 1 through 9 exactly once. Every properly made Sudoku puzzle has exactly one valid solution.
Yes. The Daily Challenge generates one puzzle per calendar day, so every visitor who plays that day is solving the exact same board. It resets at midnight and keeps a running streak of how many days in a row you've solved it.
Yes — it's completely free with no account or sign-up required. Practice puzzles are unlimited across Easy, Medium, Hard, and Expert difficulty.
Start by scanning each 3×3 box, row, and column for numbers that only have one possible cell left. Use pencil-mark notes to track candidate numbers in emptier cells, and look for naked pairs to eliminate numbers elsewhere. Our strategy guides work through every technique with diagrams.