Sudoku at a glance
Fill the 9 by 9 grid so every row, every column and every outlined 3 by 3 box contains the digits 1 through 9 exactly once. Printed clues stay fixed. Every puzzle here has one verified solution and can be completed with logic rather than guessing.
Rules and objective
- Each row must contain the digits 1 through 9 with no repeats.
- Each column must contain the digits 1 through 9 with no repeats.
- Each outlined 3 by 3 box must contain the digits 1 through 9 with no repeats.
- Starting clues cannot be changed. Fill every empty square correctly to finish the puzzle.
- In Killer Sudoku, the digits in each dotted cage must also total its small target, without repeating a digit inside the cage.
Select a square and use the number pad or keyboard. Notes record possible candidates; Check flags conflicts; Hint explains a logical next step before filling it.
Strategy: a dependable solving routine
Scan the busiest units first
Rows, columns and boxes with the fewest empty squares have fewer possibilities. List what is missing, then test each open square.
Write candidates, not guesses
Use notes when a square has two or more possibilities. Remove candidates as numbers appear in the same row, column or box.
Look for hidden singles
A digit may fit several squares at first glance, yet have only one legal position within a particular row, column or box.
Re-scan after every placement
One solved square changes three units at once. Before moving to a harder technique, check its row, column and box again.
Frequently asked questions
Do I need to guess?
No. Every included puzzle has a unique solution and is matched to a logical technique set for its difficulty.
How does Killer Sudoku work?
Follow all standard Sudoku rules, then make each dotted cage add up to its target without repeating a digit inside that cage.
What do the difficulty levels mean?
Higher levels introduce progressively more advanced deductions, from singles through pairs, locked candidates, X-Wing, Swordfish and forcing contradictions.
Will my progress be saved?
Yes. The current puzzle, notes, undo history and preferences save on this device when browser storage is available.