Wordoku is a free online Sudoku played with letters instead of numbers. Every row, every column and every box must hold each of the board's letters exactly once, and those letters are the letters of one word: when the puzzle is finished, one row or column spells it out, and that line lights up gold the moment you fill it correctly. Tap a square and pick a letter from the pad, or just type it. Pencil in notes, undo, and use up to three hints that explain their reasoning. Twelve levels run from 4×4 grids with four-letter words, through 6×6, to full 9×9 boards with nine-letter words, and every board is generated by the game, has exactly one answer and is solved by logic alone before you see it. No download, no account.
How to play Wordoku
- The grid is split into boxes by the heavy lines: 2×2 boxes on a 4×4 board, 2×3 boxes on a 6×6 board and 3×3 boxes on a 9×9 board. The letters in black are given and cannot be changed.
- Fill every empty square with one of the letters on the pad so that every row, every column and every box holds each letter exactly once.
- Tap a square to select it, then tap a letter on the pad, or type the letter on a keyboard. The digit keys pick the pad's letters in order, the arrow keys move the gold cursor, and Backspace or the ⌫ key clears a square. Tapping the letter a square already holds takes it off again.
- Turn on Notes (or press Space) to pencil small candidate letters into a square instead. Writing a letter in a square clears that letter from the notes in its row, column and box.
- A letter that appears twice in a row, column or box turns red, so a clash shows at once.
- The board's letters are the letters of one word, which is spelled left to right along one row, or top to bottom down one column, of the finished grid. The Hidden word strip shows question marks until you fill that line correctly; then the line lights gold and the word appears.
- The puzzle is solved the moment every square is filled and no letter clashes. Undo steps back, Clear removes everything you added, and New Puzzle deals another board and word on the same level.
- The ? button fills one square and says why: a wrong letter is put right first, otherwise it fills the next square that can be worked out from the board. Three per board.
Tips
- Start with the letter that appears most often among the givens. Look at each box where it is missing: when the rows and columns it already sits in leave only one square in that box, it goes there.
- Work square by square too. If a square's row, column and box already hold every letter but one, that last letter is the answer — that is the step level 5, 8 and 9 boards need.
- From level 10, use notes. When a letter's only places in a box all lie in one row, it cannot go anywhere else in that row outside the box — rub it out of those notes.
- On level 12 look for pairs: two squares in one row, column or box that can only take the same two letters. Those two letters belong to those two squares, so cross them off every other square in that line or box.
- Try to guess the hidden word from the pad's letters, but do not trust it to fill a line until it fits the grid: the word could run along any row or any column.
FAQ
Is Wordoku free to play?
Yes. It runs in the browser with no download, no sign-up and nothing to buy. All twelve levels are included and unlock as you solve them, and New Puzzle deals more boards on any level you have reached.
What is Wordoku?
Wordoku is Sudoku with letters in place of digits. The rules are the same: every row, column and box holds each symbol once. Here the letters are the letters of a word with no repeated letter, and that word is spelled out along one row or column of the finished grid.
Do I need to know the word to solve the puzzle?
No. Every board can be solved from the Sudoku rules alone, without knowing the word. The word is a bonus: the Hidden word strip shows question marks until you have filled its row or column correctly, and then reveals it.
Does every puzzle have exactly one answer?
Yes, and it is checked rather than assumed. Each board is built from a complete grid, and a solver that only makes forced deductions — never a guess — must finish it before it is shown, which means there is only one answer. The tests also count every possible answer by brute force and find exactly one.
Will I ever have to guess?
No. Levels 1 to 4, 6 and 7 need only one step: a letter with just one square left in a row, column or box. Levels 5, 8 and 9 also need a square with just one letter left. Levels 10 and 11 need letters that line up inside a box, and level 12 needs pairs of squares that share the same two letters.
How many levels are there?
Twelve. Levels 1 and 2 are 4×4 grids with four-letter words, levels 3 to 5 are 6×6 grids with six-letter words, and levels 6 to 12 are full 9×9 grids with nine-letter words, with fewer given letters and harder steps as you go.
Does Wordoku work on mobile?
Yes. Tap a square, then a letter on the pad under the board; the board fills the width of a phone held upright. On a computer you can play with the mouse or entirely from the keyboard.
How is this different from the Sudoku on this site?
The logic is the same, but the symbols are letters, the boards come in 4×4 and 6×6 sizes as well as 9×9, and one line of every answer spells a hidden word, so finishing a board ends with a word as well as a full grid.