Become an expert sudoku solver with a free online puzzle game. Check the calendar, complete daily sudoku challenges and earn badges. Use a variety of options to tailor the gameplay for you to enjoy sudoku puzzles online for free. For instance, you may use notes and list the possible digits in a particular cell. You can also change the highlighter color to suit your mood. Finally, you may change the UI language. The puzzles alternate in difficulty, so the game offers both easy and hard sudoku levels. By the way, the possibility to solve sudoku puzzles on your phone makes it one of the most popular commuter games.