Privacy

Internet Sudoku is designed to work without accounts. Puzzle progress, preferences, and daily streaks are saved locally in your browser so you can continue where you left off. Leaderboard entries use an anonymous browser identity and public generated name instead of an account.

Local storage

The app uses localStorage to save puzzle entries, notes, mistake count, timer progress, hints used, pause state, selected cell, daily completion streaks by date, difficulty, and completion timestamp, an anonymous leaderboard identity, the generated public leaderboard name, and simple game settings such as highlighting and note cleanup. Undo history is kept only in memory for the active session and is not written to localStorage. This local game state stays on your device and is not tied to a login.

Anonymous leaderboard

When a puzzle is completed, Internet Sudoku may submit the generated public name, anonymous player identifier, puzzle date, difficulty, completion time, hints used, mistakes, and calculated score to build daily, weekly, and speed-run leaderboards. Leaderboard records are retained for 14 days by default.

Cookies and accounts

Internet Sudoku does not require an account and does not use cookies for game state. Clearing this site’s browser data removes saved puzzles, settings, streaks, and the anonymous leaderboard identity on that device.

Sharing links

The copy link button only copies the canonical puzzle URL for the visible daily puzzle. It does not include your progress, notes, or settings.

Analytics

Internet Sudoku uses Vercel Analytics to understand broad site usage. Analytics is not used to collect puzzle entries, notes, mistakes, timer progress, streaks, or saved game state.