Five difficulties, notes and unlimited undo, and hints that give you the reasoning instead of the answer. Nothing to install, nothing to sign into — it runs in the browser.https://play-sudoku.coenhttps://play-sudoku.cohttps://play-sudoku.coFive difficulties, notes and unlimited undo, and hints that give you the reasoning instead of the answer. Nothing to install, nothing to sign into — it runs in the browser.Sat, 05 Sep 2026 00:00:00 GMTFive difficulties, notes and unlimited undo, and hints that give you the reasoning instead of the answer. Nothing to install, nothing to sign into — it runs in the browser.https://play-sudoku.co/daily-challengehttps://play-sudoku.co/daily-challengeOne new puzzle a day, and everyone who arrives that day solves the same one. Your browser builds it from the date rather than asking a server, so there is nothing to log into.Sat, 05 Sep 2026 00:00:00 GMTOne new puzzle a day, and everyone who arrives that day solves the same one. Your browser builds it from the date rather than asking a server, so there is nothing to log into.https://play-sudoku.co/tournamenthttps://play-sudoku.co/tournamentThree new puzzles on the first of every month, and everyone who shows up that month solves the same ones. Race a field of 100 and keep the rank you finished with.Sat, 05 Sep 2026 00:00:00 GMTThree new puzzles on the first of every month, and everyone who shows up that month solves the same ones. Race a field of 100 and keep the rank you finished with.https://play-sudoku.co/ruleshttps://play-sudoku.co/rulesThe three rules for filling a 9×9 grid, plus what row, column, box, clue and candidate mean. There is no arithmetic anywhere; every cell is settled by logic alone.Sat, 05 Sep 2026 00:00:00 GMTThe three rules for filling a 9×9 grid, plus what row, column, box, clue and candidate mean. There is no arithmetic anywhere; every cell is settled by logic alone.https://play-sudoku.co/how-to-playhttps://play-sudoku.co/how-to-playFrom naked singles to Swordfish, the thirteen techniques this hint searches in order of difficulty, one line each. Every technique has its own page worked through with an example.Sat, 05 Sep 2026 00:00:00 GMTFrom naked singles to Swordfish, the thirteen techniques this hint searches in order of difficulty, one line each. Every technique has its own page worked through with an example.https://play-sudoku.co/awardshttps://play-sudoku.co/awardsTwelve badges for finishing each difficulty, for puzzle counts, for days in a row and for your best times. Nothing is sent to a server, so there is no leaderboard — it all stays in this browser.Sat, 05 Sep 2026 00:00:00 GMTTwelve badges for finishing each difficulty, for puzzle counts, for days in a row and for your best times. Nothing is sent to a server, so there is no leaderboard — it all stays in this browser.