Sudoku Solver
Enter any Sudoku puzzle and solve it instantly, or watch the solution unfold step by step with technique explanations.
How to Use the Sudoku Solver
Enter Your Puzzle
Type the given numbers into the 9×9 grid. Use arrow keys to navigate quickly between cells. Leave unsolved cells empty.
Choose Solve Mode
Click "Solve Instantly" for the complete solution, or "Step by Step" to learn the techniques used.
Learn & Improve
In step-by-step mode, each move is explained using real Sudoku techniques — from basic singles to advanced patterns.
Free Online Sudoku Solver
Our Sudoku solver is the fastest way to solve any 9×9 Sudoku puzzle online. Whether you are stuck on a newspaper puzzle, want to verify your solution, or want to learn advanced solving techniques, this tool has you covered. Simply enter the given numbers into the grid and choose how you want to solve it.
The "Solve Instantly" mode uses our advanced solving engine to find the complete solution in milliseconds. The solver applies 12 different techniques — from basic Naked Singles and Hidden Singles to advanced patterns like X-Wing, Y-Wing, and Swordfish.
The "Solve Step by Step" mode is where the real learning happens. Instead of showing the answer all at once, it walks you through each move using the exact technique a human solver would use. Every step includes a clear explanation of why a number goes in a specific cell, helping you build the skills to solve puzzles on your own. Check out our complete guide to playing Sudoku and top solving tips to accelerate your learning.
How Our Sudoku Solver Works
Unlike basic solvers that rely solely on brute-force backtracking, our Sudoku solver uses the same logical techniques that expert human solvers apply. The engine first scans for simple deductions like Last Free Cell and Naked Singles, then progressively applies more advanced strategies such as Naked Pairs, Pointing Pairs, and Box/Line Reduction. For the hardest puzzles, it employs master-level patterns including X-Wing, Y-Wing, and Swordfish before falling back to backtracking only when no logical deduction remains.
After solving, the engine analyzes which techniques were required and assigns a difficulty rating based on the hardest technique used. This means you can enter any puzzle and instantly learn whether it's a beginner-friendly Naked Singles puzzle or a grandmaster-level Swordfish challenge — making it a powerful study tool for improving your own skills.
Solver Features
- Instant solving — Get the complete Sudoku solution in under a second with a smooth wave animation
- Step-by-step mode — Watch each move explained with the exact technique used, perfect for learning
- 12 solving techniques — From Last Free Cell to Swordfish, every strategy is demonstrated and linked to its guide
- Difficulty analysis — See a breakdown of every technique required and the puzzle's overall difficulty rating
- Real-time conflict detection — Highlights duplicate numbers in the same row, column, or box as you type
- Keyboard navigation — Use arrow keys to move between cells quickly for fast puzzle entry
- Input validation — Checks for minimum clues (17) and detects unsolvable or invalid puzzles before solving
- No registration required — Completely free, ad-free, and works on any device with a browser
When Should You Use a Sudoku Solver?
- Verify your solution — Check if you solved a puzzle correctly
- Learn new techniques — Watch the step-by-step solver to discover strategies you haven't tried
- Get unstuck — When you hit a wall, see the next logical move and understand why it works
- Study puzzle difficulty — See which techniques are required for a given puzzle
- Speed practice — Compare your solving path with the optimal solution
Frequently Asked Questions
Is the Sudoku solver free to use?
Yes, our Sudoku solver is completely free with no ads or registration required. Enter any standard 9x9 Sudoku puzzle and get an instant solution or step-by-step walkthrough.
Can the solver handle any Sudoku puzzle?
Our solver can handle any valid 9x9 Sudoku puzzle, from easy to expert difficulty. It uses advanced techniques including Naked Singles, Hidden Singles, X-Wing, Swordfish, and brute-force backtracking as a fallback — so it can solve every solvable puzzle.
Does the solver show the solving steps?
Yes! Click "Solve Step by Step" to see exactly which technique is used for each move. The solver highlights the relevant cells and explains the logic behind every step — perfect for learning new solving strategies.
What techniques does the solver use?
The solver uses 12 progressive techniques: Last Free Cell, Naked Single, Hidden Single, Naked Pair, Pointing Pair, Box/Line Reduction, Hidden Pairs, Naked Triple, Note Validation, X-Wing, Y-Wing, and Swordfish. Each technique is explained when used in step-by-step mode.
Can I paste a puzzle from another source?
Yes! You can type numbers directly into the grid using arrow keys to navigate, or click "Paste puzzle string" below the grid to import a puzzle as an 81-character string — use digits 1-9 for given numbers and 0 or . for empty cells.
What if my puzzle has no solution?
If the puzzle you entered is invalid or has no solution, the solver will let you know immediately. Double-check your input for typos — a single misplaced number can make a puzzle unsolvable.