Who makes this site
freeprintablesudoku.com is run by Alex K., a sudoku solver who got tired of printable puzzle sites that take five clicks to print one grid, hide the answers behind an email form, or publish puzzles with more than one solution. This site is the fix: open a page, press Print, done.
How the puzzles are made
Every puzzle is generated by our own engine rather than copied from a puzzle book. The process is the same for every level:
- The engine fills a complete valid grid at random.
- It removes digits one at a time, in symmetric pairs on 9x9 grids, checking after each removal that the puzzle still has exactly one solution and still stays within the target level. Easy and medium puzzles keep a minimum number of given digits so they stay approachable.
- Two independent solvers then check the result. The first is a brute-force solver that counts solutions; it must find exactly one. The second solves the puzzle the way a person would, using named techniques, and records the hardest one it needed.
- Only puzzles that pass both checks are published. If the solvers disagree about the answer, or the logical solver cannot finish, the puzzle is discarded.
The printed set on each page is generated once a day when the site is rebuilt. On the 4x4, 6x6 and 9x9 pages the same engine and the same checks run in your browser when you press New puzzles or change the layout. Samurai puzzles take far longer to generate, so they are made and checked in advance and only loaded when you ask for them.
How difficulty is graded
We grade by the hardest technique a puzzle requires, not by how many digits are given:
- Easy: naked singles only. There is always a square with a single possible digit.
- Medium: needs at least one of hidden single, naked pair, hidden pair, pointing pairs or triples, or box-line reduction, and nothing harder.
- Hard: needs at least one of naked triple, hidden triple, X-Wing, Swordfish or XY-Wing, and nothing harder.
Puzzles that would need forcing chains or guesswork are not published at all.
Puzzle IDs
The short code under each grid, for example 9E-7F3A2C1D, is the puzzle’s ID. It records the grid size, the level and the seed the engine used, so the same ID always produces the same puzzle; 4x4 and 6x6 IDs start with 4 and 6, for example 4E-7F3A2C1D. Samurai IDs start with S instead of a grid size, for example SM-7F3A2C1D. If you report a problem, that code tells us exactly which puzzle you mean.
What we do not do
No accounts, no email gates, no pop-ups, no puzzles with hidden second solutions. New 4x4, 6x6 and 9x9 puzzles and every PDF are generated in your browser, and samurai puzzles are fetched from a stock we prepared in advance. Nothing you print is sent anywhere.
Using the puzzles
You are welcome to print as many sheets as you like for yourself, your family, your classroom or your care home. Please do not sell the sheets or republish the puzzles as your own.
Contact
Email contact@freeprintablesudoku.com. There are a few tips on what to include on the contact page.