Hard Sudoku Online
Hard Sudoku puzzles that need pencil notes and techniques like pairs and pointing, and still have one logical solution.
How do you play Hard Sudoku?
A hard Sudoku has few numbers filled in. Pencil in the possible numbers for every empty square. Then use pairs: two squares in a unit that share the same two numbers. Use pointing too: when a number in a box can only sit in one line, remove it from the rest of that line.
Sudoku rules
- The grid has 9 rows, 9 columns and nine 3 x 3 boxes. Some numbers are already filled in.
- Fill every empty square with a number from 1 to 9.
- Each row, each column and each 3 x 3 box must contain every number from 1 to 9 exactly once.
- Every puzzle has exactly one solution, and you can always find the next number by logic.
- A wrong number counts as a mistake. After three mistakes, you can watch a short ad for one more chance.
Hard Sudoku tips
- Fill in notes for every empty square before you look for harder steps.
- Find pairs. If two squares in a row, column or box can hold only the same two numbers, remove those numbers from the other squares there.
- Use pointing. If a number in a box fits only in one row or column, it cannot go elsewhere in that row or column.
- After each new number, update your notes at once. Old notes hide the next step.
More ways to play Sudoku
Hard Sudoku questions
How do you solve a hard Sudoku?
Pencil in all possible numbers, then use pairs and pointing to remove notes until a square has one number left. Repeat until the grid is full.
What is a pair in Sudoku?
Two squares in the same row, column or box that can hold only the same two numbers. Those two numbers can be removed from the other squares in that row, column or box.
What is pointing in Sudoku?
When a number inside a box can go only in one row or column of that box, it can be removed from the rest of that row or column outside the box.
Do hard Sudoku puzzles need guessing?
No. Every puzzle here has exactly one solution and can be solved by logic. It is free and never uses real money.
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