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Sudoku duel — a two-player race

Two players, one puzzle, at the same time. You never see your opponent’s digits, only how far along they are. The server checks every answer: right ones stay, wrong ones count as mistakes. First to fill the board wins.

Online duelPlay solo

Free · no sign-up · phone and desktop

Duel: the board and both players’ progress

The rules

  • You both get the same puzzle; the first to fill every cell wins.
  • The server checks each digit. Three wrong answers lose the game. An obvious clash on the board does not count: the game simply refuses that tap.
  • If nobody finishes in 20 minutes, the fuller board wins; equal means a draw.
  • Your notes are yours alone. There are no hints or undo: this is a race.
  • If you lose your connection, come back within 2 minutes and your board will be waiting. Otherwise your opponent wins.

Finding an opponent

  1. Quick match. Pick a level (Easy, Medium or Hard). If someone is waiting there, the game starts right away. If nobody is, we say so plainly: we do not use fake opponents. You can wait, play solo or call a friend.
  2. With a friend. Create a 4-character code and send the link on Telegram. The game starts as soon as your friend opens it or types the code.

Elo rating

Everyone starts at 1200 Elo. In the first 20 games it moves faster (K = 40), then slower (K = 20). Beating an equal gains 20, a stronger player more. Resigning early before any answer does not count. The rating reflects skill alone: there is no money, no prize and no privilege.

How to be fast

  • Digit first, then cells: tap a digit’s key and then each cell it belongs in. That beats choosing a digit for every cell.
  • Do not place a digit you are unsure of: the third mistake ends the game. A quick note costs less.
  • If your opponent’s percentage climbs fast, do not rush: the last 20% is usually the easiest, while the middle is where people get stuck.

FAQ

Can my opponent see my digits?

No. The server sends only your percentage and mistake count. The solution is never sent to either of you: it stays on the server.

What if no opponent shows up?

You can wait in the queue, but you do not have to: one tap takes you to solo play or lets you send a friend a code. There are no fake players.

Is the game lost if the server restarts?

No. The state is saved during a deploy, clients reconnect by themselves and your board comes back.

Which levels have duels?

Easy, Medium and Hard. Expert and Master take too long for a race, so they are for solo play.

See also

Sudoku onlineSudoku onlinefree, no sign-upDaily sudokuDaily sudokuthree a day, with a leaderboardSudoku techniquesSudoku techniquessingles to X-Wing, with examplesHard sudokuHard sudokuHard, Expert, Master
Online duel