Sudoku
Play Sudoku free online: classic 9×9 grid, 3 difficulties, notes, timer and auto-validation. No download, pure logic — fill rows, columns and boxes with 1-9!
More games to play
How it works
Play, earn points and Retro Coins: the shared currency across every RetroPlayNow game. Unlock badges and climb the leaderboard! Your progress is saved automatically on this device.
Sudoku is the world's most beloved logic puzzle and it lands on RetroPlayNow in its perfect 9×9 form. Every row, every column and every 3×3 box must contain the digits 1 to 9 exactly once. No math, no guessing — just pure deduction.
Our generator builds a fully solved board with backtracking and then carves a puzzle with a guaranteed unique solution for your chosen difficulty: Easy (42 clues), Medium (32 clues) or Hard (26 clues). Tap a cell and use the number pad or your keyboard (1-9, Backspace, arrows). Toggle pencil notes to jot candidates, get instant error highlighting, and watch the timer climb as you reason your way to the finish.
Finished in fewer seconds and with fewer mistakes for a higher score and more Retro Coins. Your best time per difficulty is saved on this device, so you can chase personal records. Whether you have two minutes or an hour, Sudoku is the timeless brain workout — no daily limit, endless fresh puzzles.
How to play Sudoku
- Pick a difficulty. Choose Easy, Medium or Hard from the top bar. A fresh 9×9 puzzle is generated instantly.
- Fill 1-9 in every row, column and box. Each row, column and 3×3 box must contain digits 1-9 exactly once. Givens are fixed.
- Select a cell and enter a digit. Click/tap a cell or move with arrows, then tap the number pad or press 1-9. Backspace/0 erases.
- Use notes for candidates. Toggle ✏️ Notes to pencil small candidates in a cell. Great for hard puzzles.
- Finish clean for more points. Complete the grid — conflicts turn red instantly. Faster time and fewer errors mean higher score and more Retro Coins.
Frequently asked questions
How do you play Sudoku?
Fill the 9×9 grid so every row, column and 3×3 box contains digits 1-9 exactly once. Use logic to deduce where each number goes.
What are the difficulty levels?
Easy has 42 clues (more givens), Medium 32 and Hard 26. Fewer clues means harder deduction and a higher target score.
Can I take notes?
Yes — toggle Notes (or press N) and then tap digits to add small pencil candidates inside a cell. Toggle off to write big answers.
How is the score calculated?
Base 10,000 minus time (seconds×2) and mistakes (×100), plus a 500-point clean bonus if you finish with zero errors. Best score per difficulty is saved.
Is Sudoku free and mobile-friendly?
100% free, no download. Tap cells and the number pad, or use keyboard 1-9/arrows/Backspace. Works perfectly on phones and tablets.
