What is Wordoku?
Wordoku (sometimes called letter sudoku or word sudoku) is sudoku played with letters instead of the usual digits. The rules are exactly the same — every row, column and box must contain each letter exactly once — but there’s a bonus mystery baked in: the letters aren’t random. They all come from one secret word, and when you solve the puzzle, that word appears spelled out along the main diagonal, from the top-left corner down to the bottom-right.
Every puzzle on this page hides a different kid-friendly word — it might be an animal, a colour, a season or something from a fairy tale. The letter bar above the board shows you which letters are in play (in alphabetical order, so they don’t give the word away). Guessing the hidden word early doesn’t solve the puzzle for you, but it’s a brilliant clue for the diagonal squares!
If your child has already played our 4×4 sudoku or 6×6 sudoku, the rules will feel instantly familiar — Wordoku just swaps digits for letters. It also pairs nicely with Color Sudoku and Space Sudoku, which swap the digits for colours and space friends instead.
Three sizes, one page
Use the size tabs above the board to switch grids any time — your progress in each size is saved separately, so you can hop between them without losing a thing.
- 🐣 **4×4** — a 4-letter word (like STAR or FROG) in a tiny 16-square grid. Perfect for ages 4–6 and very first puzzles.
- 🌱 **6×6** — a 6-letter word (like ROCKET or DRAGON) in a friendly 36-square grid. Great for ages 6–8.
- 🌳 **9×9** — a 9-letter word (like DRAGONFLY or SNOWFLAKE) in the full classic grid. The real Wordoku challenge, for confident spellers.
The 3 super-simple rules
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Every row uses every letter
A row is a line going across the grid. Each row must contain all of the puzzle’s letters, with no repeats.
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Every column uses every letter
A column is a line going down the grid. Each column must also contain all of the letters, with no repeats.
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Every box uses every letter
The grid is split into boxes (2×2 on the small grid, 2×3 in the middle, 3×3 on the big one). Each box must contain every letter exactly once.
How to play step by step
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Pick your size
Tap 4×4, 6×6 or 9×9 above the board. Each size hides its own secret word.
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Tap an empty square
The square highlights and shows which row, column and box it belongs to.
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Pick a letter from the pad
The letter buttons live next to the board, one for each letter of the hidden word. Tap the one that fits and it drops into the square. On a keyboard, just type the letter.
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Use Notes for tricky squares
Tap ✏️ Notes to jot tiny "maybe" letters in a square, or Auto Notes to fill every possibility in automatically.
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Need help? Tap Hint
The Hint button reveals the correct letter for the selected square. Hints count in your stats, but they’re always there when you need a boost.
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Finish and reveal the word
When the last letter lands, the diagonal lights up and the hidden word is revealed. Can you guess it before the grid is full?
Easy strategies for kids
- 🔍 Find the row, column or box with the most letters already filled in — it’s the easiest to finish
- 🔤 Pick one letter and scan the whole grid for it — every row, column and box needs it exactly once
- ✏️ Use Notes to mark "maybe" letters before committing to one
- 🕵️ Watch the diagonal — if you can guess the hidden word, the diagonal squares almost fill themselves
- ✅ Tap Check whenever you feel unsure — it counts wrong letters without spoiling where they are
Solved a few and want more variety? Try the same logic with numbers in our classic 9×9 sudoku, or with pictures in Shape Sudoku and Space Sudoku.
Why Wordoku is great for kids
Wordoku gives kids everything classic sudoku does — logical thinking, planning ahead, careful checking and that proud "I did it myself!" feeling — plus a gentle literacy boost. Kids practise recognising letters, holding them in memory and unscrambling them into a real word, all while they think they’re just playing a game.
It’s also a lovely bridge puzzle. Kids who love reading but shy away from numbers often try Wordoku first and then discover that classic sudoku is exactly the same game. And early readers get to feel like word detectives: the moment the hidden word appears on the diagonal is a genuine little celebration.
For parents and teachers
Every puzzle is generated with exactly one solution and can always be finished with pure logic — no guessing needed. The hidden words are hand-picked to be kid-friendly: animals, nature, food, colours and everyday favourites. Because each letter must be different, the words also make nice spelling practice — every word uses each of its letters exactly once.
The game saves progress automatically on the device, one save per grid size, so a half-finished puzzle is waiting after dinner. There’s no signup, no chat, and it plays comfortably on phones, tablets and laptops — including a mouse-free keyboard mode with arrow keys and letter typing.
Frequently asked questions
What is Wordoku?
Wordoku is sudoku played with letters instead of numbers. Every row, column and box must contain each letter exactly once. On this page every puzzle also hides a secret word, which appears along the main diagonal when the puzzle is solved.
Is Wordoku harder than normal sudoku?
No — the logic is identical, because the letters are just symbols like the digits 1–9. Some kids actually find letters friendlier than numbers, and the hidden word gives an extra clue that numbers can’t: if you guess the word, you know the whole diagonal.
What ages is Wordoku for kids suitable for?
The 4×4 grid works from about age 4–5 with a grown-up nearby, the 6×6 suits ages 6–8, and the 9×9 is great from around 8 and up. Kids who can recognise letters can play — they don’t need to be strong readers.
How do I find the hidden word?
Solve the puzzle! The word is spelled along the main diagonal, from the top-left square down to the bottom-right square. The letter bar above the board shows the letters in alphabetical order, so you can also try to unscramble the word as you play.
Can I switch between the 4×4, 6×6 and 9×9 grids?
Yes — use the size tabs above the board. Each size keeps its own saved game, so switching never loses your progress.
Is Wordoku for kids free?
Yes, completely free. No signup, no downloads, no in-app purchases. Open the page and play — it works on phones, tablets and computers.
Does every Wordoku puzzle have exactly one solution?
Yes. Every puzzle is generated and checked so there is exactly one solution, and you can always reach it step by step with logic alone.
Try other sudoku games
Different look, same friendly logic. Pick a sibling puzzle to play next.