Fill the grid so every row, every column, and every 3×3 box contains the digits 1 through 9 exactly once — that's the whole rulebook, no other constraint applies. Tap a cell, then pick a digit from the pad or your keyboard; the game flags any digit that already appears in that row, column, or box, so a mistake is visible before it costs you. Not ready to commit? Turn on notes to pencil in candidates for a cell, the same way you would on paper. Every puzzle here is machine-checked to have exactly one solution before it ever reaches your screen, so there's always a next logical step to find — solving is never a guess, on any difficulty.
Difficulty here is about which techniques a puzzle forces you to use, not how many clues it starts with. Easy puzzles fall to singles — cells and digits with only one place they can go. Medium adds locked candidates and naked pairs, small deductions that trim your options. Hard expects pairs, triples, and the occasional X-Wing, a pattern across two rows or columns that rules out candidates elsewhere. Expert is evil-tier: XY-Wings and Swordfish, chains of logic that take a few passes to see. Every tier is solvable by pure reasoning — no guessing required, including on Expert. Start with Easy if you're new, or jump straight to Expert if singles bore you.
No account, no download, no cookies — this loads and plays in your browser, and your progress lives there too. Every grid, from Easy to Expert, is verified to have exactly one solution before it's served, so a hard puzzle is never actually broken. Difficulty labels mean what they say, tested against the techniques a puzzle requires rather than a clue count. There's a fresh daily puzzle for anyone who wants a shared challenge, and printable sheets for anyone who'd rather solve on paper.
Yes. Every puzzle is machine-verified to have exactly one solution before you see it. If it's on your screen, there is one way through — and it's findable.
No. Every puzzle, including Expert, can be solved by logic alone — the hardest ones need advanced patterns like X-Wings and Swordfish, but never a coin flip. If you're stuck, there's always a next step to find.
The techniques it forces you to use — not the number of starting clues. An easy puzzle falls to singles; an expert puzzle makes you hunt wings and fish. That's also why our difficulty labels stay honest from one puzzle to the next.
At midnight UTC, everyone in the world gets the same new puzzle. The week ramps up: easy on Monday and Tuesday, medium midweek, hard on Friday and Saturday, expert on Sunday. Your streak counts days you finish the daily.
No. It's free, with no signup and no cookies. Your progress, stats, and streak live in your browser.
Yes — the printable page makes clean sheets at any difficulty, answers included on a separate page. Your browser's print dialog can save them as a PDF.
The same game on a 6×6 grid with digits 1 to 6 — boxes are two rows by three columns. It plays in a few minutes and is a friendly on-ramp for kids and newcomers.