A LITTLE FOCUS. A CLEARER DAY.
Fresh puzzles. Understandable hints. Room to think.
Start small. Notice a pattern.
Let the next number find its place.
Arrow keys to move · 1–9 to enter · Backspace to erase · N for notes
CHECK YOUR OWN GRID
Enter a puzzle, check its solution count, then take it to the board for explained steps.
Enter exactly 81 digits (0–9) or dots.
Your puzzle has not been checked.
WHAT THE RESULTS MEAN
Only checked unique puzzles can enter Play or Print. Search is capped at two solutions, 500,000 nodes and two seconds; the worker also has an eight-second safety limit.
The solver does not label a search guess as a logical hint. If singles run out, we say so.
LESS GUESSING. MORE NOTICING.
Three small guides, written for the way you actually solve.
Fill every row, column and outlined box with each digit exactly once. In a 9 × 9 grid, that means 1 through 9. The digits are labels; you never add or multiply them.
Start with a busy row. Write down its missing digits, then cross out anything already in the cell’s column or box. What remains is that cell’s candidate set.
4 × 4 uses 1–4 and 2 × 2 boxes. 6 × 6 uses 1–6 and 2 × 3 boxes. 9 × 9 uses 1–9 and 3 × 3 boxes.
Try a small grid ↗A single: one cell has only one candidate. If a 4 × 4 row contains 1, 2 and 4, its last cell must be 3. Check the column and box too; conflicting clues do not create a valid deduction.
A hidden single: one digit has only one possible place in a row, column or box. Imagine a row’s empty cells have candidates {1, 3}, {1, 2}, and {1, 2}. Only the first cell can be 3, even though it has two candidates.
Our hints recalculate candidates from the current board, show the rule and let you apply one verified placement. Notes you type are personal reminders; they are never used as proof.
When these two rules cannot progress, the board may need another technique or search. That is an engine limit, not proof of a “hard” puzzle.
Practice both rules ↗A 6 × 6 puzzle has six rows, six columns and six rectangular boxes. Each box is two rows high and three columns wide. The wide box borders help you keep those regions straight.
Scan for the digit that is missing from a crowded box, then compare its possible cells with their rows and columns. A shorter digit list makes this a useful place to learn candidate notation.
For paper practice, select 6 × 6 in Print, choose A4 or US Letter, and build up to six original puzzles. Each puzzle gets its own spacious page. Answer pages are separate and use the exact same puzzle IDs.
Build a 6 × 6 booklet ↗Small grids can make a relaxing activity feel cramped. Our print layout uses one puzzle per page, a 170 mm square grid and bold box boundaries. Digits scale with the chosen grid size.
Select your printer’s actual paper size and print at 100% scale. Leave “fit to page” off unless your printer needs it. Answer keys follow the puzzle pages, so you can leave them face down.
Print the current puzzle to keep its original givens, or make a seeded booklet. Playing a few numbers does not silently change the printed puzzle or its answer.
Make room to think ↗ONE SKILL AT A TIME
Original examples with replayable candidate evidence. No timer, no streak pressure.
A HABIT TO KEEP
Before you place a number, finish this sentence: “This must be ___ because ___.” If the reason is just a hunch, keep looking.
Practice boards come from this site’s seeded generator and pass the same uniqueness check as play puzzles. The highlighted placement is checked against candidates before it is shown.
TAKE A LITTLE QUIET WITH YOU
Original, large print Sudoku booklets for A4 or US Letter. Answers included, on separate pages.
One 170 mm grid per page. A matching answer page for every puzzle. Booklets are limited to six puzzles per run.
Prepare your booklet to preview and download it.