Free online Sudoku
Classic Sudoku 16x16
Classic Sudoku 16x16 is a focused grid for practicing row, column, and box logic without losing track of the board. Choose a difficulty, solve in the browser, and switch to another size when you want a different pace.
Current board
16x16 Sudoku for long sessions, advanced scanning, and extended candidate work.
Play Classic Sudoku 16x16 online with 4x4 boxes, symbols 1-9 and A-G, and a clear grid for focused logic practice.
Grid
16x16
Box
4x4
Symbols
1-G
16x16 SudokuMedium
Classic Sudoku keeps the familiar row, column, and box logic while changing the grid size for fast practice or longer challenges.
Classic Sudoku board
Medium · 16x16-medium-001
Entry deck
Keep digit entry, pencil marks, undo, redo, clear, and conflict scan beside the grid.
Focus a playable cell
Select a cell to begin.
Train every row, column, and box
Classic Sudoku 16x16 keeps the logic visible: each row, column, and 4x4 box uses 1-G once, so every placement has a clear reason.
Every symbol has one place
The answer is not guessed. Scan missing symbols, compare the crossing units, and use pencil notes only when the board still has two or three real candidates.
Scale the practice without changing the rules
Use compact boards for warmups and larger boards for longer sessions. The same row, column, and box rule stays in place, while the solving pace changes.