Master Sudoku
Free online Sudoku — easy through extreme. No download, no login required. New puzzle every session.
Master Sudoku - For Serious Puzzle Enthusiasts
Master puzzles require you to chain multiple techniques together in sequence. Individual deductions no longer suffice - You must build logical chains where each elimination enables the next.
Master puzzles are specifically constructed so that no single technique creates a full cascade of solves. Every breakthrough opens a path that immediately reaches another constraint - You must alternate between several techniques, often within the same chain of reasoning.
| Technique | Complexity | What It Achieves |
|---|---|---|
| Naked/Hidden Singles | ★☆☆☆ | Direct cell placement |
| Naked/Hidden Pairs, Triples | ★★☆☆ | Candidate elimination in units |
| Pointing Pairs / Box Reduction | ★★☆☆ | Cross-unit elimination |
| X-Wing / Swordfish | ★★★☆ | Multi-row/col fish elimination |
| XYZ-Wing | ★★★☆ | 3-cell pivot eliminates shared candidate |
| Simple Colouring | ★★★☆ | Chain-based contradiction detection |
| Remote Pairs | ★★★★ | Long chain of identical 2-candidate cells |
| Finned X-Wing / Swordfish | ★★★★ | Extended fish with extra "fin" cells |
- Pick a candidate digit and trace all cells where it appears in chains of strongly-linked pairs (cells that see each other and share only that candidate in their mutual unit).
- Colour alternating cells in the chain - Say, blue and green.
- Colour trap: If two cells of the same colour see each other, that colour is impossible - Place the other colour in all its cells.
- Colour wrap: If an uncoloured cell can see both a blue and a green cell, that candidate is eliminated from the uncoloured cell regardless of how the chain resolves.
- This technique unlocks cells that no fish or pair technique can touch.
- Work the grid in layers: basic eliminations → pairs/triples → fish → chains
- Never advance to the next layer until the current one is fully exhausted
- Keep notes meticulously - A missed elimination at step 2 invalidates all work in steps 3–4
- When stuck, look for the digit with the fewest remaining unsolved instances - Usually 3 or 4 - As a chain candidate
- Review the Sudoku Solving Techniques guide for visual walkthroughs of each method
Realistic solving times by experience at this level:
| Factor | Expert | Master |
|---|---|---|
| Given cells | 22–28 | 18–24 |
| Chaining required | Rarely | Regularly |
| Colouring techniques | Not needed | Often needed |
| Avg dead-ends hit | 0–1 | 2–5 |
| Time commitment | 30–60 min | 45–90 min |
Why Sudoku.by?
6 Difficulty Levels
Easy to Extreme - Every level carefully tuned to challenge you just the right amount.
Killer Sudoku
Add cage sums to the classic formula for an extra layer of logical deduction.
Try Killer SudokuSave Your Progress
Create a free account to save, pause, and resume your games across any device.
Create AccountDaily Challenges
A new puzzle every day. Beat your personal best and see how you rank globally.
Today's ChallengePrintable Sudoku
Generate print-ready puzzle sheets for any difficulty. Perfect for commuting or classrooms.
Print Master PuzzlesLearn Techniques
From Last Free Cell to X-Wing - Master every solving technique in our rules hub.
View All TechniquesFeatured Variants
View all 30+ variants →Latest from the Blog
View all posts →Live Scores
Full Leaderboard →| Player | Score | Time | Difficulty | Type | Completed |
|---|---|---|---|---|---|
| Loading scores… | |||||
Updates every 30 seconds