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Your pace.
Your kind of quiet.
A quiet place for a good puzzle
Play free classic Sudoku online on Random.Express. Fill the nine-by-nine grid using logic, with comfortable mobile controls, a daily puzzle, and light or dark themes. No download or account is required.
How to play Sudoku
Each row, column, and outlined three-by-three box must contain 1 through 9 exactly once. The bold starting clues stay fixed. Tap a cell and then a number; use Notes to mark possibilities. Focus Grid enlarges any box without needing browser zoom.
Choose your challenge
Beginner uses straightforward single-candidate placements. Easy introduces hidden singles, Medium uses locked candidates, and Hard adds pairs. Expert reaches X-wings or deductions beyond this logical solver. Ratings reflect solving techniques, not just how many clues are shown.
Notes, hints, and saving
Notes use a small three-by-three candidate grid. Undo and redo restore entries and notes together. Hints first highlight a cell, then explain a deduction, and only enter a digit when you ask. Unsupported deductions are labeled as answer reveals.
Your ordinary puzzle and Daily puzzle save separately in this browser. An optional Random.Express account can sync progress with explicit conflict choices.
Comfort after dark
Eight themes include Graphite, Midnight Blue, OLED True Black, Warm Night, and Dark High Contrast. Choose a layout independently. The timer is off and the game is silent by default. Flat surfaces and event-driven updates keep the game idle while you think.
True-black surfaces may reduce display power on OLED screens; results depend on your display.
Can I play without a timer or mistake penalty?
Yes. The timer is optional and disabled by default. There is no mistake limit or game-over penalty. Checking can be Off, Conflicts only, or Against solution.
How is the daily puzzle selected?
A local calendar date selects one deterministic Medium puzzle and transformation. Everyone using the same calendar date receives the same board, without an external puzzle service. Missing a day never removes progress.