Sudoku Online
A unique grid in this tab. Pencil marks, undo, and a hint that names the move. Daily is the same seed for everyone. No ads and no account.
Loading the first grid.
A grid that is ready when the page is
Search for sudoku online and the first tap is often a video, a store wall, or a hint that wants a weekly plan. I wanted the other thing: a unique grid in this tab, pencil marks on the first screen, and a hint that says why a cell is a 7.
This page opens on a solvable board. You can start typing. New Puzzle and Daily sit next to the grid. There is no account. The current board stays in this browser until you clear it. Press Learn if you have never filled a grid. It starts with the goal, lights the given numbers, then one row, one column, and one box. After that it picks an empty cell and shows which digits that cell's houses already used. Arrow keys move the selection. Digits fill. N toggles notes. U undoes. H asks for a hint. On a phone the pad under the grid does the same work.
Four difficulties, one published method
A clue count alone is a weak label. Two 30-clue grids can ask for very different work. This page classifies a puzzle by the hardest named technique that finishes it. Solvable with naked singles only. Usually 42 to 54 given cells. Needs hidden singles after naked singles run out. Usually 32 to 41 given cells.
Needs a naked pair or a pointing move. Usually 26 to 31 given cells. Unique, but the named beginner techniques do not finish it. Usually 22 to 25 given cells. If a seed cannot make that class, the page says so and you can try again. Times only mean something next to the hint count and the pauses. A three minute expert with four hints is not the same run as a three minute expert with none.
Hints that talk, and stay free
Hint looks at the current board. If a cell has one candidate, it says naked single and fills it. If a digit has one seat in a row, column, or box, it says hidden single. A naked pair or a pointing move is named the same way. When those run out, it tells you it is using the unique solution, not a fancier name I did not implement.
Undo walks back fills, notes, and hints. Pencil marks are a toggle on the pad. Auto notes is a setting, off by default, and it only writes candidates for empty cells.
Daily is a shared seed, not a feed
Daily is medium, seeded from the UTC date. A friend in another timezone still gets the same board that calendar day. Share copies a link with the date, or with the 81 givens for a random puzzle. The solution stays here. The page shows a short link. Copy share link puts the full URL on the clipboard. A friend who opens that link gets the givens, never the filled cells.
After a finish you get the clock, the hint count, and the pause count. There is no rank and no global list. If you want another quiet game in this tab, Wheel Spinner and Random Name Picker are already live. The longer write-up is The Hint Sat Behind a Paywall.
What this page will not do
It will not sell a hint. It will not put an ad between two puzzles. It will not invent a second solution and call the grid fair. Every new board is checked for exactly one solution before you see it. A pasted share link that is not unique is rejected.
Mixpanel sees that you opened sudoku, changed difficulty, or finished. It does not see the digits. Clear saved game wipes the local board and the settings on this machine.
Common questions
Does this puzzle leave my browser?
The grid is built and checked in this tab. A new puzzle, a hint, undo, and the daily seed all run in JavaScript here. After the page has loaded you can unplug the cable and keep playing. Softery.io does load Mixpanel and Google Analytics on every page, including this one. Those calls never get the grid. They get a difficulty name, a time band, and a hint band.
How do you decide easy versus expert?
By the hardest named technique that finishes the grid, not by a private score. Easy is naked singles only. Medium needs hidden singles. Hard needs a naked pair or a pointing move. Expert is still unique, and those named moves do not finish it. Clue counts sit next to that rule so you can see both.
What does a hint actually tell me?
It names a cell, a digit, and the technique. Naked single, hidden single, naked pair, or pointing. If none of those apply, it says the grid has one solution and fills one cell from that solution. Hints are free. The clock keeps running, and the result card shows how many you used.
Can I play the same daily puzzle as a friend?
Yes. Daily uses the UTC calendar date as the seed, so the medium grid is the same for everyone that day. Share copies the date or the givens. It never copies the solution. The page shows a short link. Copy share link puts the full URL on the clipboard.