Sudokoi

Free Sudoku for thinkers. No ads, no nags, no lockouts. Daily puzzle plus four difficulties, hints that explain the technique, and a board built to be calm and relaxing.

Sudokoi started from one question: what if a sudoku app actually respected the player? The ones that dominate the store today are built to maximize taps — to interrupt, to nudge, to monetize the next 30 seconds of your attention. Sudokoi is built for the opposite: a single quiet puzzle, played at your own pace, that's still waiting for you when you come back.

WHAT'S INSIDE

• Four new daily puzzles every day • Four difficulty tiers — Easy, Medium, Hard, and Nightmare — generated, then verified by a human-style technique solver so the ratings are honest • Corner notes, center notes, and auto-erase across peers (or turn that off and pencil it yourself) • A "Fill Notes" shortcut for when you'd rather skip the bookkeeping • Hints that don't just point at a cell — they explain the technique. Naked Single. Hidden Pair. X-Wing. Y-Wing. The hint sheet shows the digits, the cells, and the reasoning, so the next puzzle gets easier • A non-punitive mistake counter. We track if you placed a wrong digit, but we never lock you out or end the game • Per-difficulty stats: best time, average time, games won • Music, sound effects, and haptics — all optional, all togglable in Settings

WHAT'S NOT INSIDE

• No ads. Not banners, not interstitials, not "watch an ad to continue." Nothing. • No 3-strikes-and-out. No restart-from-scratch. • No identity tracking. We use anonymous diagnostics to tune defaults and you can turn even that off in Settings. • No subscription. Sudokoi is free. If we ever add paid features, they'll be additive — your daily puzzle, your four difficulties, and your stats stay free forever.

THE ENGINE

Sudokoi's puzzles come from a backtracking generator that produces a unique solution for every grid, then verifies the difficulty with a logical solver — the same code that powers the hints. The solver knows every standard sudoku technique through Jellyfish and beyond, which is why Hard and Nightmare actually feel like Hard and Nightmare.

ONE PERSON, IN THE OPEN

Sudokoi is built by one person. The privacy policy and terms are honest documents you can actually read at sudokoi.com. Feedback goes to a real inbox at feedback@sudokoi.com and gets a real reply.

If you've ever wished a sudoku app would just shut up and let you solve, this one's for you.