Which characters can I use?
Most Sudoku variants accept multiple character sets. The solver automatically detects which set you are using based on your input.
| Grid size | Numbers | Letters | Mixed | Hex |
|---|---|---|---|---|
| 5 | 1–5 | A–E | — | — |
| 6 | 1–6 | A–F | — | — |
| 7 | 1–7 | A–G | — | — |
| 8 | 1–8 | A–H | — | — |
| 9 | 1–9 | A–I | — | — |
| 10 | 1–10 | A–J | — | — |
| 11 | 1–11 | A–K | — | — |
| 12 | 1–12 | A–L | 1–9, A–C | — |
| 14 | 1–14 | A–N | 1–9, A–E | — |
| 15 | 1–15 | A–O | 1–9, A–F | — |
| 16 | 1–16 | A–P | 1–9, A–G | 0–9, A–F |
| 18 | 1–18 | A–R | — | — |
| 20 | 1–20 | A–T | — | — |
| 21 | 1–21 | A–U | — | — |
| 22 | 1–22 | A–V | — | — |
| 24 | 1–24 | A–X | — | — |
| 25 | 1–25 | A–Y | — | — |
Custom sets — Besides the predefined sets above, the solver accepts any set of unique characters, as long as exactly N different characters appear on the board (where N is the grid size).
Odd-Even Sudoku only accepts numbers because the parity constraint (odd/even) only applies to digits.
The solver detects the character set automatically — just make sure all entries on the board use the same set.