Play Sudoku Online — Free, Honest, and No Guessing
Classic 9×9 Sudoku with three promises most apps won't make. Every puzzle is solvable by pure logic — a solver verifies it start to finish before you see it. Difficulty is honest — it names the hardest technique the puzzle actually requires, not a star count. And the built-in coach teaches instead of telling: it names the technique, then shows you where, then walks the logic — but it never fills a cell for you. Play right now, free, no download and no account.
How to play Sudoku
- Fill the grid so every row, column and 3×3 box contains the digits 1–9 exactly once.
- Tap a cell then a digit — or tap a digit first and paint it into cells (the fast solver's way). The same pad serves both.
- Flip the ✎ Notes toggle (or press N) to pencil small candidate marks. They always sit in the same 3×3 spot inside the cell, so pairs jump out when you scan.
- A wrong entry gets the reason ("9 already sits in this box at R2C7"), not just red ink.
- Fill all 81 cells correctly to solve it — then read the review to see where your time went.
Honest difficulty: the technique ladder
- Easy — singles. Every step is a naked or hidden single: one digit, one home. Perfect for learning to scan.
- Medium — pairs & pointing. Adds naked/hidden pairs and triples, and pointing/claiming eliminations between boxes and lines.
- Hard — X-wings. Somewhere in the solve an X-wing or XY-wing is genuinely required — the generator verifies it.
Because the solver grades each puzzle by the hardest technique it needs, "Hard" here means hard for a reason you can learn, never "we removed more clues and hoped".
A coach that teaches, never tells
Tap 💡 Coach once: "There's a naked pair in row 4." Again: it rings the cells. A third time: the full plain-language walkthrough — "R4C2 and R4C7 can only be 3 or 8, so no other cell in row 4 can be either." You choose how much help to take, and the cell is never filled for you. The coach even reads your own pencil marks: if your notes already show the pair, it says so — and if a stale note is hiding a single, it points that out too.
Guess detection — rewarding logic, not luck
The solver knows at every moment which cells are provable. Fill a cell that wasn't provable yet and the review flags it — even when the digit was right. Turn on Strict coach in settings to hear about it immediately. Solve with no coach and no guesses and the summary awards the line that matters: solved unaided.
The post-solve review
Solving is the start; the review is the lesson. Using per-move timestamps it shows where you stalled ("you spent 4:10 here — the way out was an X-wing in columns 2 and 7"), where you guessed, and whether a sloppy pencil mark caused the stall. Even on a clean win it shows your longest think and the deduction that was waiting there.
Frequently asked questions
- Is this Sudoku game free?
- Yes — completely free, in your browser, with no download, no account, and no stakes of any kind.
- Do the puzzles ever require guessing?
- Never. Every puzzle has exactly one solution and is verified solvable start-to-finish using only its difficulty's techniques.
- What are training wheels?
- An optional assist (off by default) that maintains all candidate marks for you. It's honestly labelled — auto-notes quietly do the first layer of solving — and the summary reports which notes mode you solved with.
- Can I play a daily Sudoku?
- Yes — one shared board per day for everyone, on a weekday ladder: Monday–Tuesday Easy, Wednesday–Friday Medium, weekends Hard. Your streak is tracked per game.