solution lookup
Sudoku answers: look up the solution to any puzzle
Type the code printed under a puzzle to see its solution, whether you are stuck or checking a finished grid. You need no answer key and no account.
How the lookup finds the answer from a six-character code
The site has no database, and you never uploaded your puzzle. The code works as a compressed copy of the puzzle, so the lookup can rebuild it without storing anything.
Generating a sudoku involves a lot of shuffling: which digits go where in the first complete grid, and in which order the generator removes clues. A single starting number drives all of that shuffling. Fix the number and the generator runs the same way each time, down to the last cell. The code carries the difficulty you chose and that starting number, and from those two the generator rebuilds your puzzle, and its solution, on the spot.
Codes do not expire, so a sheet you print today will still look up in ten years, because the lookup recomputes the answer. And the lookup runs in your browser like the rest of this site, so nobody, including us, learns which puzzles you have been working on.
We designed the codes to resist typos. They leave out the letters I, L, O and U, so you cannot confuse them with 1 and 0, and each code carries a small built-in check. If you get a character wrong, the page tells you the code is wrong instead of showing the answer to a different puzzle.
Where to find the code
Look under the grid. Each puzzle prints its code on the left, a hash followed by six characters, with the difficulty and clue count on the right. On a sheet with four or six puzzles to a page, each grid has its own code, so you can look up one puzzle without spoiling the rest of the page.
To get the answers on paper from the start, use printable sudoku with answers, which puts a full key at the back of the PDF. Use this page when you did not print a key or have lost it.
Looking up answers: questions
Where do I find the puzzle code?
Under the grid, to the left of the difficulty. It has six characters after a hash, like #K7M2A9, and each puzzle on the sheet has its own.
How can it know the answer without storing my puzzle?
The code works as a recipe for the puzzle. The generator turns a code into a grid by a fixed procedure with no randomness in it, so entering the same code rebuilds the same puzzle and its solution from scratch. We never received your puzzle, so we had nothing to store.
Does this work for a sheet I printed months ago?
Yes. Codes do not expire, and no database can go stale, because the code holds everything the lookup needs. A sheet you find at the back of a drawer in five years will still work, as long as you can read the code.
It says the code is not one we could have printed. What now?
You have most likely misread a character. Codes leave out the letters I, L, O and U so you cannot confuse them with 1 and 0. If you read one of those letters, try the digit. A check built into each code makes the lookup reject a wrong entry instead of showing you someone else’s puzzle.
Can I still get the answers printed in the PDF?
Yes. Tick "Include answers" in the generator and the solutions print as a section at the back of the document. The option starts unticked, since most solvers prefer a clean set of puzzles and look up the odd answer here.
Can I link straight to a solution?
Add the code to the address: /sudoku-answers?code=K7M2A9 opens with that puzzle solved. Use it when you set puzzles for other people and want to send the answer separately.
Need more puzzles?
The free printable sudoku generator makes a fresh set at any difficulty, including runs that mix levels. If you are checking a grid because you got stuck, the solving techniques guide can get you moving again without giving away the answer.