The rules
Fill the 9×9 grid so that every row, every column, and every 3×3 box contains the digits 1–9, each used once. Some cells are given. You never need to add or multiply — only to notice where a digit is still allowed.
A move is wrong if any house (row, column, or box) contains the same digit twice.
How a game on soduku.net works
- Select a cell, then a number — or pick a number first and stamp it into empty cells.
- Notes pencils candidates into a cell. N toggles that mode.
- Auto-check (on by default) paints a digit red if it doesn’t belong in the unique solution. Three mistakes end the round; you can take a second chance.
- Hint names the next technique and fills the cell.
Techniques that actually matter
Naked single
A cell has only one candidate left: every other digit already lives in its row, column, or box. Place it. Easy puzzles are almost all of these.
Hidden single
Inside one house, a digit can go in only one remaining cell — even if that cell still has other candidates. The digit is hidden among the notes. Place it.
The “third box”
If a digit already appears in two of the three boxes in a band, the third copy must sit in the remaining box. Scan those nine cells.
Beginner habits
- Start with houses that already hold five or more givens. The leftovers are often singles.
- Pencil marks are cheaper than guesses. Fill notes, then hunt hidden singles.
- Don’t guess on this site’s puzzles — every board has one solution and can be finished by logic.
Elsewhere on the site
Play a timed game with six difficulties. Print today’s five puzzles for paper. Solver walks a stuck grid one named move at a time.