Free Sudoku Online
100% FreeNo sign-upBest Easy: —. Tap a cell then a number, or use your keyboard. Notes, mistakes and your best all stay in your browser.
Play free Sudoku online — choose easy, medium, hard, expert or extreme, and solve a fresh puzzle any time. Every board is generated and verified in your browser to have a single solution, with pencil notes, hints, mistake checking, a timer and automatic save so you can pick up where you left off.
What is Sudoku?
Sudoku is a logic puzzle played on a 9×9 grid divided into nine 3×3 boxes. The goal is to fill every empty cell so that each row, each column and each box contains the numbers 1 to 9 exactly once. A well-made puzzle has exactly one solution and never requires guessing.
How to play Sudoku
Start with the numbers already placed. Look for rows, columns or boxes that are nearly full and work out which digit must go where. Tap a cell and enter a number, or use pencil notes to track the candidates for a cell until you can be sure.
Sudoku difficulty levels
Easier puzzles begin with more given numbers, so they can be solved with simple scanning. As difficulty rises, fewer clues are given and you will need techniques like hidden singles, pairs and pointing pairs. Expert and Extreme are a serious challenge for experienced solvers.
Tips to solve Sudoku faster
Scan for a number that appears often and find where it can still go. Use notes to shrink the candidates in each box, then look for a cell where only one candidate remains. Highlighting matching numbers and the current row, column and box makes patterns much easier to spot.
Daily Sudoku and your stats
A new daily puzzle is coming to Zerdly, with the same board for everyone that day and a streak for solving it. Your best times per difficulty are saved locally on your device — Zerdly never sees your games.
Frequently asked questions
How do you play Sudoku?
Fill the 9×9 grid so every row, every column and every 3×3 box contains the digits 1 to 9 exactly once. Some numbers are given to start; work out the rest using logic — no guessing required.
Is every Zerdly Sudoku solvable?
Yes. Every puzzle is generated in your browser and verified to have exactly one solution, so it can always be solved by logic alone.
What do the difficulty levels mean?
Harder levels start with fewer given numbers, so they need more advanced techniques. Easy and Medium are great for a relaxed solve; Hard, Expert and Extreme are for experienced players.
What are pencil marks / notes?
Notes let you pencil in the candidate numbers for a cell. Turn on Notes mode, then tapping a number adds or removes it as a small mark instead of placing it.
Is it free?
Completely free, with no account and no download. Everything runs in your browser and nothing is uploaded — your game, notes and best times stay on your device.