Numbers
Sudoku Generator
Every puzzle here starts life as a fully solved, valid 9x9 grid — every row, column, and 3x3 box containing the digits 1 through 9 exactly once — built by rotating and shuffling a known-valid base pattern so each generated grid is genuinely different. From that completed solution, the generator removes a set number of cells to create the puzzle you actually solve, with more cells removed at higher difficulty settings. Easy puzzles keep more of the grid filled in as a scaffold, while expert puzzles strip it down to the bare minimum and lean on you to work out the rest through deduction. The output gives you both halves: the puzzle grid with periods marking empty cells, and directly below it the complete solution grid, so you can check your work or just play digitally without needing a separate answer key. Difficulty is set purely by how many cells get removed, not by guaranteeing a single unique solution path — that requires a full backtracking solver, which this generator skips in favor of speed. In practice the puzzles are still solvable and challenging at every difficulty tier; if you want competition-grade puzzles with a provably unique solution, treat this as a fast practice generator rather than a tournament source.
How to use
- Choose your options above
- Click Generate
- Copy your result
Detailed instructions
- Choose a difficulty level: easy, medium, hard, or expert.
- Click the generate button to build a fresh, valid 9x9 puzzle grid.
- Read the puzzle rows top to bottom, where each period marks an empty cell you need to fill in.
- Use the bars in each row to identify the 3x3 box boundaries while solving.
- Scroll to the "— Solution —" section to check your answer once you've finished, or to reveal it if you're stuck.
Use Cases
- •A teacher printing a fresh easy-difficulty sudoku puzzle every morning as a warm-up activity for a math class
- •A puzzle app developer generating sample grids at four difficulty levels to test how their solver UI renders filled and empty cells
- •Someone on a long flight generating an expert puzzle to pass the time without needing to bring a physical puzzle book
- •A parent creating a medium-difficulty puzzle for a kid learning logical deduction for the first time, using the solution to check their answer afterward
- •A puzzle-newsletter writer generating several hard puzzles to hand-pick the one with the most interesting empty-cell layout for that week's issue
Tips
- →Start with easy or medium difficulty if you're new to sudoku — the extra starting digits make the early deduction steps much more approachable.
- →Scan each 3x3 box, row, and column for the digit that has the fewest possible empty cells left to place it in — that's usually the fastest next move.
- →Cover the solution section with your hand or a piece of paper while solving if you don't want to risk an accidental spoiler glance.
- →Generate a new puzzle immediately if the one you get looks too sparse or too easy for your taste — every click produces a completely different grid.
- →Use expert difficulty puzzles for timed solving practice, since the minimal starting clues force you to rely on chained logical deductions rather than quick scans.
FAQ
is the generated puzzle guaranteed to have only one solution
No — this generator removes cells based on the difficulty level without running a uniqueness check, since verifying a single solution requires a full backtracking solver. In practice most generated puzzles are solvable through normal logical deduction, but on rare grids at higher difficulty there could technically be more than one way to fill in the empty cells.
how do I read the puzzle format with the dots and bars
Each row is written left to right with a period standing in for an empty cell and every number shown as-is. The vertical bars mark the boundaries of the 3x3 boxes, splitting each row into three groups of three digits, exactly like the bold grid lines on a printed sudoku puzzle.
Why does the solution appear right after the puzzle?
It's included so you can check your work without leaving the page or hunting down a separate answer key. If you want to solve without spoilers, just don't scroll down to the "— Solution —" section until you've filled in the grid yourself.
What is the actual difference between easy and expert difficulty?
The only variable is how many cells get cleared out of the completed grid before it's handed to you — easy removes the fewest cells, leaving more starting digits as scaffolding, while expert removes the most and leaves you with very few given numbers. Fewer starting clues generally means more deduction steps and more branching to work through.
can I get a puzzle with a specific set of starting numbers
No — every puzzle is randomly generated from a shuffled valid grid, so you can't specify exact starting digits or a particular layout. If you don't like the puzzle you get, just generate again; it costs nothing and produces a completely different grid each time.
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