Sudoku Atlas: 4x4-25x25

Sudoku Atlas is 25x25 Sudoku — and 16x16, 9x9, 6x6, and 4x4 — fully offline. No ads, no tracking, one-time unlock. Play a free daily 9x9, or open a real 25x25 grid (625 cells). Same rules at every size. EVERY GRID SIZE From quick 4×4 and 6×6 warm-ups to the classic 9×9, all the way up to sprawling 16×16 and 25×25 marathons. The full spectrum, from two-minute breaks to multi-day challenges. A FREE DAILY PUZZLE THAT NEVER EXPIRES A new 9×9 every day, free forever, no account required. Difficulty cycles through easy, medium, hard, and maximum. The free version isn't a teaser: it includes a demo bank of puzzles across every grid size and difficulty so you can try everything before you decide. FOCUS MODE Pick a cell and every value but one blurs away, placed digits and pencil marks alike. Your chosen number stays crisp so you can scan the whole board and see exactly where it can still go. STAMP MODE Lock a digit and stamp it across the board in one motion. Pencil marks for candidates, glyph stamps for confident answers. Switch freely between them. CHECKPOINTS Save your board at any point and rewind if you hit a dead end. Try bold moves without fear of losing progress. SEED SHARING Every puzzle has a seed code. Share it and a friend gets the exact same grid in the exact same starting state. Race, compare, collaborate. LIGHT, DARK & HIGH CONTRAST Follows your system appearance and language by default. Light, dark, high-contrast themes and language can all be set manually. NO ADS. NO TRACKING. ONE PURCHASE. There is no ad SDK in this app. No analytics, no crash reporters, no account system, no server that knows you exist. Everything runs on your device and stays there. One purchase unlocks unlimited generation, all grid sizes, and seed sharing, with no subscription, ever, and no previously free feature will ever move behind a paywall. These aren't marketing promises. They're structural decisions, and they're permanent.