Play Sudoku free in your browser. Three difficulty levels. Fill the 9x9 grid with numbers 1-9. No download required.
A standard sudoku presents a 9x9 grid divided into nine 3x3 boxes. Some cells are pre-filled as clues. Fill every empty cell with a digit from 1 to 9 such that each digit appears exactly once in every row, every column, and every 3x3 box. No arithmetic is involved. The puzzle is entirely about logical deduction from the constraint that no digit repeats in any row, column, or box.
Start by scanning for naked singles: cells where only one digit remains possible given the row, column, and box constraints. Next look for hidden singles: a digit that can only appear in one cell within a given row, column, or box, even though other digits are also possible there. These two techniques alone solve most easy and many medium puzzles. For harder puzzles, learn naked pairs, where two cells in a unit share the same two candidates, allowing those digits to be eliminated from other cells in that unit.
Modern sudoku was developed by Howard Garns, an American architect, and first published in 1979 under the name Number Place. The puzzle gained massive popularity after being rediscovered and refined in Japan during the 1980s and returned to the English-speaking world via British newspapers in 2004, triggering a worldwide craze. Today it is the most widely published logic puzzle on earth, appearing daily in thousands of print and digital outlets in dozens of languages.
The three difficulty buttons control how many cells are emptied from a fully solved grid: Easy removes 30 cells, Medium 45, and Hard 55. Every puzzle is verified to have exactly one solution before it appears, so you never need to guess blindly. The grid is also randomized each time by shuffling rows and columns within blocks and remapping the digits 1-9, meaning no two puzzles repeat. There is no timer or move limit; the only pressure comes from the error counter in the top-right corner, which ticks up whenever you place a digit that conflicts with the same row, column, or box. Choosing a difficulty immediately generates a fresh board, so switching mid-game starts over. Beginners should clear several Easy boards before Medium, where naked and hidden singles still carry most of the work.
This board gives instant visual feedback as you fill cells. Tap or click a cell to select it (it highlights blue), then enter a digit with the on-screen number pad or your keyboard. A correctly placed digit that breaks no row, column, or box rule shows in blue; a digit that conflicts with an existing entry turns red and adds one to the error count. Pre-filled clue cells stay shaded and cannot be changed. Press Delete or Backspace, or tap the erase key, to clear a selected non-clue cell. Use the red entries as a live check: if a number turns red, the conflict is somewhere in that cell's row, column, or 3x3 box. The puzzle is won automatically the moment every cell is filled and the whole grid is valid.
Fill the 9x9 grid so every row, every column, and every 3x3 box contains the digits 1-9 exactly once. The shaded numbers shown at the start are fixed clues. Select an empty cell, then type or tap a digit to fill the rest.
Easy leaves 51 given numbers (30 removed), Medium leaves 36 (45 removed), and Hard leaves 26 (55 removed). Fewer clues force you to rely on harder deduction chains. Every level still guarantees a single unique solution, verified before the board appears.
Red means the digit conflicts with an identical number already present in that cell's row, column, or 3x3 box. It also adds one to the error counter at the top right. Erase it with Delete, Backspace, or the erase key and try a value that fits all three units.
Yes. Clicking any difficulty button, or the restart button after winning, generates a brand-new randomized grid. The board reshuffles rows, columns, and digit mappings each time, so you will not see the same puzzle twice in normal play.
No. This Sudoku has no timer and no game-over state. The error counter simply records how many conflicting entries you made, letting you track accuracy, but it never ends the game. You can take as long as you like to finish the board.