Play Free Sudoku Online (2025)

Master the grid with Sudoku Monster, the #1 web app for free sudoku puzzles. Enjoy unlimited daily challenges, from Beginner to Monster Hard. No download required.

Explore Sudoku Levels

What is Sudoku?

Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 subgrids contain all of the digits from 1 to 9.

Sudoku Monster generates unique puzzles instantly using a backtracking algorithm and Latin Square permutations, ensuring every game is fresh.

How to Play: The 3 Rules

ElementConstraint
RowMust contain numbers 1-9 exactly once.
ColumnMust contain numbers 1-9 exactly once.
Box (3x3)Must contain numbers 1-9.

Daily Sudoku Challenge

Join thousands of players today in our Daily Sudoku Challenge. Solve a unique, hand-picked puzzle every 24 hours and maintain your streak. Compete on global leaderboards.

Is Sudoku Good for Your Brain?

Yes! Regular play improves memory, concentration, and logical thinking. It reduces anxiety by providing a structured mental workout.

Sudoku Strategy Guide

Learn advanced techniques like Scanning, Naked Pairs, and X-Wings to solve even the hardest Evil Sudoku levels. Use our built-in Note Mode to track candidates.

  • Scanning: Look for rows/cols that eliminate options in a box.
  • Candidate Marking: Write small numbers to track possibilities.
  • Naked Pairs: If two cells have only [2,7], remove 2 and 7 from the rest of the row.

Sudoku Glossary

Cell
A single square in the grid.
House
A row, column, or 3x3 box.
Candidate
A potential number for a specific cell.
Given
Numbers provided at the start of the puzzle.

Sudoku Monster is fully responsive, works offline via PWA, and requires no download. Join thousands of players today.

Frequently Asked Questions

How do I remove ads?
You can remove ads by purchasing the Monster Pass or the one-time No Ads unlock.
Is Sudoku Monster free?
Yes, the core game is 100% free to play online.

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