Play Sudoku online.
Easy to Expert puzzles.
The classic 9×9 logic puzzle, right in your browser. Four difficulty levels, pencil notes, hints, mistake checking, undo, and per-difficulty best times — all free, private and playable on any device.
Play Sudoku in 3 easy steps.
Pick a Difficulty
Choose Easy, Medium, Hard or Expert. Every puzzle is freshly generated with a guaranteed unique solution, so you never have to guess.
Fill the Grid
Tap any empty cell, then press a digit on the number pad (or your keyboard). Every row, column and 3×3 box must contain the digits 1 through 9 exactly once. Givens cannot be changed.
Use Notes & Hints
Stuck? Toggle Notes mode to pencil candidates into a cell, or press Auto to fill every legal candidate at once. The Hint buttons reveal a cell or a whole digit if you need help.
Everything you need to solve Sudoku.
Four Difficulty Levels
Easy (40 givens), Medium (32 givens), Hard (28 givens) and Expert (24 givens). Every puzzle is procedurally generated and verified for a unique solution.
Pencil Notes Mode
Toggle Notes mode to write small candidate digits inside a cell. Notes are essential for advanced techniques like naked pairs and X-Wings.
Auto-Notes Fill
One press of the Auto button fills every empty cell with all of its legal candidates, so you can start with a complete picture of the puzzle.
Two Hint Modes
Hint Cell reveals the correct digit for the selected cell. Hint Digit places every occurrence of one number you choose. Hints never count as mistakes.
Mistake Detection
Any digit that breaks the rules is immediately highlighted in red and counted in the mistake tracker, so you can catch errors the moment they happen.
Undo & Erase
Made a wrong move? Undo the last entry with a single tap, or erase the selected cell entirely. The undo history remembers your last 200 actions.
Peer Highlighting
Selecting a cell highlights its row, column and 3×3 box, and every cell containing the same digit is tinted so you can spot patterns instantly.
Timer & Best Times
The timer runs from your first move and stops when you solve the puzzle. Your best time is saved per difficulty in your browser.
Mobile Optimised
The 9×9 grid scales cleanly from desktop to phone. Digits are large tap targets, and the number pad reflows to fit any screen width.
The Free Online Sudoku
Sudoku is one of the most popular logic puzzles in the world. Played on a 9×9 grid split into nine 3×3 boxes, the goal is simple: fill every empty cell with a digit from 1 to 9 so that each row, each column and each 3×3 box contains every digit exactly once. Given cells — called givens — are already filled in and can never be changed.
What makes Sudoku special is that no arithmetic or guessing is needed. Every well-formed puzzle has exactly one solution that can be reached through pure logic. Our free Sudoku uses a solver that verifies uniqueness before presenting a puzzle, so you never have to worry about a board that has multiple valid answers.
The game ships with four difficulty levels. Easy leaves around 40 givens and can be solved with basic scanning techniques. Medium drops to about 32 givens and adds more hidden singles. Hard leaves about 28 givens and requires techniques like pointing pairs and box-line reduction. Expert leaves only 24 givens and demands advanced methods like X-Wings and swordfish.
To help you at every stage, the game includes a full toolset: pencil notes for tracking candidates, an auto-notes button that fills every legal candidate in one press, undo for the last 200 moves, and a hint system that can reveal a single cell or a whole digit. Mistake detection highlights errors the moment they happen, so you can learn from them without guessing.
Frequently Asked Questions.
Sudoku is a logic puzzle played on a 9×9 grid that is divided into nine 3×3 sub-grids (also called boxes or regions). The goal is to fill every empty cell with a digit from 1 to 9 so that each row, each column, and each 3×3 box contains every digit exactly once. A well-formed puzzle has exactly one solution that can be reached by pure logic — no guessing required.
Click or tap any empty cell to select it, then enter a digit from 1 to 9 using the number pad or your keyboard. The puzzle is solved when every row, column and 3×3 box contains the digits 1 through 9 with no repeats. Given cells (called givens) cannot be changed. Use Notes mode to mark candidate digits in a cell, and Hint if you get stuck.
Pencil notes (also called candidates) are small digits you write inside a cell to record which numbers could still legally go there. They are essential for advanced solving techniques like naked pairs, hidden singles and X-Wings. Press the Notes button (or the N key on desktop) to toggle notes mode and add or remove candidates. The Auto-Notes button fills every cell with all of its legal candidates at once.
Four: Easy, Medium, Hard and Expert. Easy puzzles leave around 40 givens and can be solved with basic scanning. Medium leaves about 32, Hard about 28, and Expert about 24 — requiring more advanced techniques like pointing pairs, box-line reduction and X-Wings.
A well-formed Sudoku should have exactly one solution. Our generator uses a solver that verifies uniqueness before every puzzle is presented. If a puzzle ever had multiple solutions it would be impossible to reach a definitive answer by logic alone, which is why every proper Sudoku must have a unique solution.
Yes. Sudoku is fully responsive and touch-friendly. Tap a cell to select it, then tap the digits on the on-screen number pad. All the tools — Notes, Erase, Undo, Hint — are accessible from the same pad. The 9×9 grid scales perfectly to fit any phone screen.
Yes. It is 100% free with no signup, no download, no ads inside the game and no hidden costs. Your best times are stored only in your browser.