🔢 Sudoku

How to play

Fill the 9x9 grid with the digits 1 through 9. Every row, column, and 3x3 box must contain each digit exactly once.

Difficulty levels

Easy starts with plenty of givens and solves with straight logic. Medium asks you to scan harder. On Hard and Expert you eliminate candidates square by square. Every puzzle has exactly one solution.

The helper buttons

Check turns any misplaced digit red. New game builds a fresh puzzle at the same difficulty. Grids are generated in your browser on the spot, so you will not run into the same one twice.

Example of a first move

Say the top-left box already holds 1, 2, 4, 5, 7, 8, and 9, leaving three empty squares for 3, 6, and the last missing digit. If the first row already contains a 6, the 6 cannot go in that row's empty square, which narrows its spot. Repeating this "where can this digit go" question across boxes is how most easy grids fall.

Techniques worth learning

• Scanning: pick a digit and check every box for where it still fits.
• Naked singles: a square with only one possible candidate left.
• Hidden singles: a digit that fits only one square in a row, column, or box.
• Pairs: two squares in a unit sharing the same two candidates rule those digits out elsewhere.
• Pencil marks: on hard and expert, note every candidate before hunting.

Variations to try

• Two-player tag team: partners alternate placing one digit each and may not overrule each other.
• Race on two phones: both start an easy grid at once; first correct finish picks dinner.
• No-check challenge: finish without tapping Check even once.
• Ladder night: solve one grid at each difficulty in a row.

Tips and mistakes to avoid

Never guess on a hard grid; one wrong digit spreads errors everywhere. Stare too long and you stop seeing obvious squares, so a short break often helps. Do not skip pencil marks on expert, and double-check boxes, not just rows.

How to read a stuck grid

When nothing obvious remains, stop scanning randomly. Count how many of each digit are already placed; the digits with seven or eight copies are usually the easiest to finish. Then look at boxes with the most givens, because fewer empty squares mean fewer possibilities. If you are still stuck, focus on a single row and list what is missing. Often a digit that seemed free in several spots turns out to be blocked by a column you overlooked.

Making it a routine

Many players enjoy one grid with morning coffee or as a wind-down before bed. Easy puzzles take a few minutes, while expert grids can stretch across an evening. Because nothing needs to be finished in one sitting, sudoku fits the gaps in a day: a train ride, a waiting room, the quiet after a party. Keeping a mental note of your usual time on each level gives you a gentle way to see progress over weeks.

Who it suits

Sudoku rewards patience more than math skill, since no arithmetic is involved at all; the digits could just as easily be letters or symbols. That makes it a good fit for anyone who enjoys quiet logic, from teenagers to grandparents. Pairs who like to cooperate rather than compete often find it one of the calmest ways to share an evening.

Why sudoku?

It is a calm break during a loud game night, or a quiet way to fill an evening alone. No opponent, no timer, no pressure: put it down and return later. Cracking one stubborn square together makes it a surprisingly good puzzle for two.

Picking a level

On easy the numbers almost announce themselves. On medium and hard you progress by ruling options out, and on expert you truly track possibilities. New players should finish a few easy grids before climbing.

If you want a small goal, try clearing each level once without the Check button in a single week.

FAQ

How do you play sudoku for beginners?

Fill a 9x9 grid so each row, column, and 3x3 box contains the digits 1 to 9 once. Start with easy puzzles, choose one digit, and look for the only square in each box where it can go. Repeat with every digit until the grid fills.

What is the best strategy for hard sudoku puzzles?

Write pencil marks listing every candidate in each empty square, then look for naked singles, hidden singles, and pairs. Eliminate digits systematically rather than guessing. On expert grids, tracking candidates carefully matters far more than speed.

Can two people play sudoku together?

Yes. Take turns placing one digit each on the same grid, or race on two phones with easy puzzles and compare times. Working together on a stuck square often goes faster, because each person notices different patterns in the rows and boxes.

Does every sudoku have only one solution?

A properly built sudoku has exactly one solution, and every puzzle generated here does. That means you never need to guess; each digit can be reached through logic if you look at the right row, column, or box.

Which sudoku difficulty should I start with?

Start with easy, where many squares are already filled and simple scanning finishes the grid. Once you solve a few without errors, move to medium. Hard and expert reward pencil marks and patience, so climb only when easy feels routine.