16×16 Sudoku Hexadoku
The giant grid: digits 1–9 and letters A–G, sixteen per row, column, and 4×4 box. Same quiet logic, four times the room.
What makes it giant
Hexadoku (also sold as super sudoku or giant sudoku) keeps every classic rule and stretches the grid to 16×16. Sixteen symbols — 1–9 plus A–G — fill each row, column, and 4×4 box exactly once. Nothing about the logic changes; there's simply more of it, and the long deductions that feel rare at 9×9 become the texture of the whole solve.
Stillgrid also plays X-Sudoku at 16×16 — both main diagonals constrained too — which is genuinely hard to find in playable form anywhere.
Rules
- Each row, column, and 4×4 box contains 1–9 and A–G exactly once.
- That's it — every classic technique carries over unchanged.
How Stillgrid plays
- Type letters directly or pick from the pad — A–G work like any digit.
- Pencil marks and auto-pencil built to stay readable with sixteen candidates.
- Cell and font scaling tuned for the big grid; best on a larger screen.
- Difficulty graded honestly by the techniques a puzzle actually requires.
- Free to play. No signup needed to play.
Common questions
What is 16×16 sudoku?
16×16 sudoku — often called hexadoku, super sudoku, or giant sudoku — is sudoku on a 16×16 grid. Instead of digits 1–9, it uses sixteen symbols, usually 1–9 plus the letters A–G, and each row, column, and 4×4 box must contain all sixteen exactly once.
How do the letters work in hexadoku?
The letters are just seven more symbols. A–G behave exactly like digits: each appears once per row, column, and box. On Stillgrid you can type letters directly or pick them from the pad, and pencil marks track all sixteen candidates.
Can I play 16×16 sudoku free on Stillgrid?
Yes. 16×16 classic and 16×16 X-Sudoku (with diagonal constraints) are free to play, with no signup needed to start a puzzle. Difficulty is graded by the techniques a puzzle actually requires.