← Play competitive Sudoku

Competitive Sudoku rules

Rules version 1 · updated 31 August 2026

Equal conditions

Both players receive the same validated puzzle, starting grid and match deadline. Ranked matchmaking begins close to your rating and widens gradually while you wait. Casual matches do not change ratings.

Result and scoring

A result counts only when the server verifies the completed 81-cell board against the selected puzzle. Completed puzzles outrank unfinished or abandoned attempts. Among valid completions, faster time scores higher and each mistake carries a visible time-equivalent penalty. Random entry therefore cannot improve a score.

Ratings

Ranked matches use Glicko-2, which tracks rating, rating deviation and volatility. New players remain provisional for their first ten rated games. The server calculates each update once; clients cannot submit rating changes.

Disconnects and abandonment

A disconnected player receives a 90-second reconnect grace period and may restore the same match with a private reconnect token. An explicit quit is an abandonment. A connection loss becomes an abandonment only after the grace period. An abandoned ranked match counts as a loss when an opponent is present.

Fair play

The service checks the final solution, timing, move validity, timer consistency and suspicious repeated pairings. Strong invalid evidence rejects a result; weaker signals are retained for review and do not create an automatic permanent ban.

Privacy

Competitive profiles use an anonymous installation identifier and a chosen public name. Country ranking is optional and uses a user-selected two-letter country—not precise GPS. See the privacy policy.