Master Sudoku Free | Very Hard Sudoku That Needs X-Wing

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What is Master level?

Master puzzles stall with everything up to Expert level (basics, pairs, pointing) and can be solved with one of the techniques below. The program checks this for every puzzle.

Techniques you'll need

X-Wing: if a number's candidates in two rows sit in the same two columns, remove it from the rest of those columns (or swap rows and columns).

Swordfish: the same idea extended to three rows and three columns.

XY-Wing: three two-candidate cells shaped AB, AC and BC let you remove C from cells seen by both ends.

Techniques for this level

X-Wing: One number, two rows, same two columns: clear it from those columns
Swordfish: One number, three rows, same three columns: clear it from those columns
XY-Wing: Pivot and two pincers clear their shared number

All Sudoku strategies →

About this level

Is Master harder than Expert?

Yes. Expert puzzles can be finished with pairs, triples and pointing. Master puzzles stall after those and need X-Wing, Swordfish or XY-Wing. Above Master come Extreme and Evil.

Do Master puzzles require guessing?

No. Every Master puzzle is checked to be solvable with techniques up to X-Wing, Swordfish and XY-Wing, and to have exactly one solution.

Difficulty levels

Level	Given numbers	What it takes
Easy	40	Fill cells that have only one possible number
Medium	32–33	Same technique, fewer clues, more searching
Hard	26–28	Use notes; pairs and pointing at most
Expert	26 or fewer	Basics always stall; pairs or pointing required
Master	28 or fewer	Pairs stall; X-Wing or XY-Wing required
Extreme	26 or fewer	Even X-Wing stalls
Evil	26 or fewer	The Extreme puzzles that need the deepest reasoning. The hardest level

How to play

1. Pick a level

Choose one of seven levels from Easy to Evil. You get a new puzzle each time.

2. Fill in numbers

Tap a cell, then a number. Each row, column and 3x3 box must contain 1 to 9 exactly once.

3. Complete the grid

Use Notes to pencil in candidates. Wrong numbers turn red.

Full rules and how to play →

FAQ

Is it free?

Yes. All seven levels are free. No sign-up.

Does every puzzle have one solution?

Yes. Each puzzle is checked by the program to have exactly one solution.

Will I lose my progress if I leave?

No. Open the same level on the same device and browser to continue. One game is saved per level.

What is the "???" button?

It's a secret stage with 3 special puzzles you won't find anywhere else (3 levels). Share, or enter the password, to open it. The password is in the share text and changes every Monday.

What are the daily stamps?

You get one stamp on each day you play. The days don't need to be in a row. Every 7th stamp is gold: it unlocks a board theme and gives you a 🎟️ mistake pass. Your stamps are saved only in this browser (no sign-up).

What is the 🎟️ mistake pass?

It lets you undo a mistake. You get one every day (use it that day) and one with each gold stamp (you can keep these). Tap the button that appears when you make a mistake. Your time still counts for the ranking.

Are there ads?

We never interrupt you with ads while you're solving a puzzle.

Can I play on my phone?

Yes. No install needed. On a computer you can also use number keys, arrow keys and N to toggle notes.

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