Sudoku Rules

The rulebook for classic Sudoku — great for settling “is that move legal?” questions.

New to Sudoku? Read How to Play. Want examples? Try the Walkthrough.

Goal

Fill the grid so every row, column, and bold 3×3 box contains the numbers 1–9 exactly once.

Board Layout

  • The board is a 9×9 grid, divided into nine 3×3 boxes.
  • Some numbers are pre-filled as givens. Those never change.
  • You fill the remaining empty cells with numbers 1–9.

Legal Moves

  • You can place any number 1–9 into an empty cell.
  • That number must not already appear in the same row, column, or 3×3 box.
  • Givens are fixed and cannot be changed.

Sudoku is a logic puzzle. You can always solve it by reasoning about what fits.

How You Win

The puzzle is solved when every row, column, and box is complete with no repeats.

Sudoku Race Rules at FFG

  • Sudoku Race uses the same classic Sudoku rules as solo play.
  • Both players get the same puzzle, and the race starts only after both players are ready and the host starts it.
  • The first correct completion wins the race.
  • Before the race starts, the guest can leave the lobby and the host can kick the guest to reopen the seat.
  • If a player gives up during a live race, the remaining active player wins.

FFG Difficulty Levels

  • Easy
  • Medium
  • Hard
  • Expert
  • Legendary

Technique Terms

You might see these terms in help, analytics, or future hints:

  • Naked Single
  • Hidden Single
  • Locked Candidate
  • Naked Pair
  • Hidden Pair
  • Naked Triple
  • X-Wing
  • Guess / Backtracking

Want a shorter version? See How to Play.