Sudoku is the classic number puzzle: fill a 9x9 grid so every row, every column and every 3x3 box uses each digit from 1 through 9 once. This version of Sudoku unblocked is built for learning as well as solving, with pencil notes, hints that explain their reasoning, six short technique lessons and five game modes. It is free, it runs in your browser, and no account is needed.
How to Play Sudoku Here
Click or tap an empty cell, then type 1 to 9 or tap the matching key on the on-screen pad. The arrow keys move the selection. Gray digits came with the puzzle and are locked in place. When you select a cell, its row, column and box are shaded, and every copy of that cell’s number lights up across the grid. Both highlights can be switched off in Settings.
Press N or click Notes to switch to pencil mode, where digits go in as small candidates instead of answers. When you place a real answer, that digit is automatically wiped from the pencil marks of every cell it can see. Erase or Backspace clears a cell, Ctrl+Z and Ctrl+Y undo and redo, P pauses, and ? shows the full list of shortcuts.
Difficulty Levels and Clue Counts
New Game opens a picker with six difficulty choices. The fewer clues you start with, the harder the logic gets:
| Level | Starting clues |
|---|---|
| Easy | 36 to 40 |
| Medium | 30 to 35 |
| Hard | 25 to 29 |
| Expert | 22 to 24 |
| Insane | 17 to 21 |
Custom has a slider from 17 up to 50 clues, so you can make a very gentle warm-up grid or pick an exact challenge. Seventeen is the smallest number of clues a standard puzzle with one answer can have.
The Five Modes and the Daily Puzzle
- Classic is a standard game with a timer that counts up.
- Zen Mode plays the same way and is meant for relaxed solving. Finishing one earns the Zen Master achievement.
- Timed Rush starts a ten-minute countdown. The game ends if it runs out.
- Hardcore allows only three counted mistakes before the game is over.
- Infinite loads a new grid at the same difficulty as soon as you finish one.
The Daily Challenge is one medium puzzle per date, the same for everyone who opens it that day. Solving it on consecutive days builds a streak, and seven in a row unlocks an achievement.
Scoring, Mistakes and Ranks
Every puzzle starts at 2,000 points. You lose 1 point per ten seconds on the clock, 100 per counted mistake and 50 per hint. By default each hint also pushes your clock forward by half a minute, or takes 30 seconds off the Timed Rush countdown. That setting can be turned off.
A mistake is counted when a digit you place is wrong and clashes with a digit already sitting in the same line or box. The clash is highlighted on the grid so you can spot it. When you finish, the results screen shows your time, accuracy, score and a rank: above 1,500 points is Expert and above 1,800 is Master.
Sudoku Tips and Strategy
- Start with the crowded areas. Any line or box with just a couple of empty cells is the fastest place to make progress.
- Track a single digit across the board. Choose, for example, the 7s, then go box by box looking for the only open spot that can still take a 7. This is the Hidden Single technique.
- Take notes once the grid gets sparse. On Expert and Insane, writing candidates shows you pairs and patterns that are invisible otherwise.
- Turn on Auto-notes for hard grids. This setting fills in every legal candidate when a puzzle starts, saving minutes of setup.
- Ask for a Level 1 hint first. It points you to the right area without giving away the digit, and costs the same 50 points as a bigger hint.
- Work through the Learn lessons. The six lessons start with singles, move on to pairs, and finish with the X-Wing and Swordfish patterns used on expert grids.
Mistakes New Players Make
The biggest one is guessing a digit because it “looks right.” A wrong guess that does not clash right away is not flagged, so it can quietly break the rest of the grid. Another is skipping notes on hard levels and trying to hold every candidate in your head. Finally, many players use hints at the first sign of trouble. Every hint costs 50 points plus time, so scan once more before asking.
Playing on a Chromebook, Phone or Laptop
The grid and number pad resize to fit the window, so it works on a small Chromebook screen, a tablet or a phone held either way. A keyboard is fastest for typing digits. Sound effects can be turned off in Settings, and six color themes, from plain Light and Dark to softer Cream, Paper, Forest and Midnight looks, let you choose what is easiest on your eyes. Since there is no time limit outside Timed Rush, you can pause a grid and come back later.
For more number logic, 2048 has you merging tiles toward bigger numbers, Number Trail asks you to draw one path through numbers in order, and Mine Field is grid logic with hidden mines. See all of them on the puzzle games page.
