Play Free Sudoku Online – From Easy to Expert
At Sudoku Star, you can enjoy free Sudoku puzzles online anytime, featuring everything from easy beginner levels to truly challenging expert grids. The site updates daily with fresh puzzles and includes a smart Sudoku solver plus optional error-checking tools to support your learning.
You can also review the basic Sudoku rules or dive into advanced solving techniques to strengthen your logical thinking and problem-solving ability. Whether you're just starting out or chasing extreme challenges, Sudoku Star is the perfect place to train your mind while enjoying classic Sudoku fun.
Basic Rules
To solve the 9×9 grid correctly, you must attain the following:
- Each Row (R1–R9) must contain all digits 1 through 9 with no duplicates.
- Each Column (C1–C9) must also include digits 1 to 9 without repetition.
- Each outlined 3×3 Block (B1–B9) must hold digits 1 to 9, each appearing only once.
For example:
- R1C1 refers to the cell at Row 1, Column 1.
- R2–R3C1 indicates the two cells in Column 1, located in Rows 2 and 3.
Useful Tips for Solving Sudoku
Always rely on logic, not guessing.
Every number you place should be supported by reasoning.
Making random selections can create contradictions and dead ends.
Minimize the amount of blanks.
Rows, columns, or 3x3 blocks with the least empty cells are the focus — these areas provide fewer alternatives and allow you to advance more rapidly.
Pay attention to the frequently filled cells.
If the number 5 has been filled in 8 cells in the grid, 5’s final position is a sure thing — there is only one possible spot left.
After every action, inspect the intersections.
After you fill a number, check the intersecting rows, columns, and blocks. New placements that you might have overlooked can be revealed. On advanced puzzles, use candidate notes to record possible numbers for each cell. They help with the identification of key patterns, Naked Pairs or Locked Candidates, that are crucial in opening further deductions.