Play Sudoku Online Free
Easy, medium and hard puzzles · Works on mobile & desktop · No download
Sudoku is a logic number puzzle played on a 9×9 grid. Your job is to fill every row, column and 3×3 box with the digits 1 to 9 so that no number repeats. No maths is needed. Just logic. Every puzzle here is freshly generated and has exactly one correct solution, in Easy, Medium and Hard difficulties.
Sudoku is free to play on PlayQuestHQ with no download and no sign-up. It works on phones, tablets, laptops and desktop computers.
Fill every row, column and 3×3 box with the numbers 1–9. Select a square, then tap a number (or type it). Wrong numbers turn red. Three mistakes and the puzzle restarts.
How to Play Sudoku
- Choose Easy, Medium or Hard.
- Fill every row, column and 3×3 box with the numbers 1 to 9, each number once.
- Select a square, then tap a number or type it on your keyboard.
- Wrong numbers turn red. Three mistakes restarts the puzzle.
- Every puzzle is freshly generated and has exactly one solution.
Controls
Click a square and type a number 1–9. Arrow keys move around, Backspace erases.
Tap a square, then tap a number on the number pad.
Tips to Win
- Start with rows, columns or boxes that already have the most numbers.
- Look for the only square in a box where a number can go.
- Selecting a number highlights the same numbers on the board. Use it to spot gaps.
- Hard puzzles need more steps of logic, not guessing.
Sudoku Rules at a Glance
Sudoku has only three rules. Fill the 9 by 9 grid so that every row, every column and every 3 by 3 box contains the digits 1 to 9 exactly once.
| Part | What it means |
|---|---|
| Row | One horizontal line of 9 squares |
| Column | One vertical line of 9 squares |
| Box | One 3 by 3 block of 9 squares |
| Givens | The digits already filled in at the start. They never change |
| Solution | The one finished grid where no digit repeats in any row, column or box |
The grid has 81 squares in total. A proper Sudoku has exactly one solution, and that solution can always be reached by logic alone, step by step, with no guessing.
How to Use Pencil Marks
Pencil marks are small notes that list every digit that could still fit in one empty square. They are the standard next step when scanning stops finding answers, because they turn guesswork into a short list of facts.
- Pick an empty square and check its row, column and box. Note every digit from 1 to 9 missing from all three.
- Every time you place a digit, remove it from the notes of all squares in the same row, column and box.
- A square left with a single note is solved. Place that digit and update the notes around it.
- Two squares in one row, column or box holding the same two notes must contain those two digits between them, so remove both digits from the notes of the other squares.
You can keep notes on paper beside the screen, or hold the key ones in your head on easier puzzles. Either way, small and current notes beat guessing.
Sudoku Solving Techniques
- Scanning: pick a number and look across rows and columns to see where it cannot go in a box.
- Naked single: a square where only one number is still possible.
- Hidden single: a number that can only fit in one square of a row, column or box, even if that square has other options.
- Pairs: if two squares in a box can only hold the same two numbers, those numbers cannot go anywhere else in that box.
Common Sudoku Mistakes and How to Avoid Them
Most failed puzzles come from a handful of repeat mistakes, and the most common is placing a digit after checking only one part of the grid. A placement is only safe when the digit is missing from the row, the column and the box.
- Checking the row but not the box: a digit can fit its row and column and still clash inside the box. Check all three every time.
- Guessing when stuck: a guessed digit can look right for many moves before the grid breaks. Scan a fresh digit or add pencil marks instead.
- Rushing the easy squares: many wrong digits go in during the first minutes, when the grid looks simple. Slow down on the squares that feel obvious.
- Working one corner only: a digit placed in one part of the grid often unlocks a square far away. Work the whole grid in rounds.
Why Sudoku Is Good for Your Brain
Sudoku uses no maths, only logic, so anyone can play it. It trains concentration, pattern spotting and patience, and short daily puzzles are a popular way to keep the mind active. Start with Easy until scanning feels quick, then move to Medium where pairs and hidden singles start to matter.
Good to Know
What is the difference between Easy, Medium and Hard Sudoku?
The difference is the number of given digits and the length of the logic needed. Easy puzzles start with more numbers filled in and fall to simple scanning. Hard puzzles start emptier and need longer chains of logic, but every puzzle at every level has exactly one solution.
Do I ever need to guess in Sudoku?
No, you never need to guess, because every puzzle here has exactly one solution that can be reached by logic alone. If you feel stuck, look again for a row, column or box where a number has only one possible square, or work through the grid with pencil marks.
What happens after three mistakes?
After three mistakes the puzzle restarts from the beginning. Each wrong number turns red and counts as one mistake, so it pays to slow down and check the row, column and box before you place a number, especially on Hard.
How long does a Sudoku puzzle take to solve?
Most players take about 5 to 10 minutes on Easy, 10 to 20 minutes on Medium and 30 minutes or more on Hard. Beginners are slower at first, and times fall quickly with practice, because you start to spot the patterns instead of searching for them.
Can I play Sudoku on my phone?
Yes, this Sudoku runs in your browser on phones and tablets as well as laptops and desktop computers, with nothing to download and no sign-up. On a touch screen you tap a square, then tap a number on the number pad, and your best scores are saved in your browser.
Is my Sudoku progress saved?
Your best scores are saved in your own browser on this device. Clearing your browser data will reset them.