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The Sudoku Book

An introduction with 101 puzzles

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Frequently asked questions





Q1. What are the rules?

There is only one rule: Every row, column and box of 3x3 cells must contain the numbers 1 through 9 exactly once.

Q2. How do I do the different size and shape puzzles?

The rules for different size and shape puzzles are pretty much identical: each row, column and group of squares enclosed by the bold lines (also called a box), must contain each number only once. In some cases the boxes are not simple squares. The different size puzzles simply require a different set of numbers (or alphabet):

Puzzle type Size Box size Alphabet
Kids 4x4 2x2 1 to 4
Kids 6x6 2x3 1 to 6
Kids/Classic 9x9 3x3 1 to 9
Monster 12x12 3x4 1 to 9, A, B, C
Monster 16x16 4x4 1 to 9, 0, A to F

Q3. Does a Sudoku have more than one solution?

Properly formed Sudokus (as available from the Daily Sudoku) always have only one solution. In our view, a Sudoku with more than one solution is not properly formed, but of course puzzles from other sources may have multiple answers.

Q4. Do I need to guess?

Sudokus from the Daily Sudoku are always solvable using logic alone. You should never have to employ trial and error tactics. Again, we can't speak for puzzles from other sources.

Q5. I'm stuck. Can you help me?

The Draw/Play option allows you to input a partially completed puzzle, and can give you a hint to help you on your way!

We get a lot of email from people who can't finish one of our puzzles. We will try and help you, but unfortunately we don't have time to reply to every query of this nature. Your best option is to ask for help in our Sudoku forums - the people there will help you far mor quickly than we can.

Q6. Your puzzle is invalid/has more than one solution.

We get a lot of email claiming that one of our puzzles is invalid or has more than one solution. So far, none of them have been correct. (What are you talking about? One has. The Monster puzzle of Nov 28th 2005 has two solutions - Ed). Before you email us with one of these claims, please check the following:

Q6. How are the puzzles graded?/Why did I find today's very hard puzzle easy?

The grading is based on the logic steps required to solve the puzzle. The requirement to use any of a number of pre-defined logic steps makes a puzzle hard, and needing "hard" logic more than a few times makes a puzzle very hard. Of course, difficulty is subjective. One person may find a particular type of logic easy, while another finds it really difficult. There are often only a relatively small number of "choke" points in even a very hard puzzle. If you happen to spot the "hard" steps quickly, then you'll fly through!

Q8. How can I print your excellent Sudoku puzzles?

PDF format files are best for printing. Click the "Printable page" link under any Sudoku grid on this site. Most browsers will automatically open the file, but if not you may need to download Acroread. If the Sudoku opens in your browser, be sure to click the print icon just above the puzzle, rather than using the "File" -> "Print" menu of your browser.

You may also be able to print any Sudoku directly from the webpage. If you find that you don't see the grid behind the numbers, try to find an option in your print settings to "print background colours and images" (or something similar).

Q9. Can I see the solution?

Sure. All puzzles in the archive have solutions available. Check back tomorrow for the solution to today's Sudoku.

Q10. The puzzle on your front/today page is out-of-date!

Some Internet Service Providers cache a local copy of pages so that your browsing experience is faster -- when you visit a page, the ISP simply retrieves it from its cache rather than the originating server. The cached page may well be out-of-date. We can't do anything about this, but most browsers have a method for forcing a refresh from the real server. In Internet Explorer, hold down the CONTROL key and hit F5. In Mozilla or Firefox, hold down SHIFT and click the "reload" button.

Q11. You used to have some blank grids available -- what happened to them?

The blank Sudoku grids are currently without a sensible home. You can download them here as PDFs for easy printing:

Q12. Is there an RSS feed for your puzzles?

There certainly is! Both the standard and kids puzzles are available in an RSS feed. Simply point your news reader at or drag the link to create a new feed.

Q13. Where is puzzle #24 from last Thursday?/Why is my answer different from yours?

Are you looking at a puzzle from the Daily Sudoku or a national newspaper? We are not responsible for the puzzles in UK newspapers. Check the links page for the relevant pages.

Q14. I don't understand your hint. Is it random?

The hint given by the Draw/Play program is the cell that the program thinks is the next logical move. Draw/Play doesn't know how to guess!

Q15. Can I save a puzzle and come back to it later?

Absolutely. Click the "save" button in Draw/Play.

Q16. I saved a puzzle - how can I retrieve it?

Simply click the "load" button in Draw/Play. Every time you save a puzzle it overwrites any previous save, so you can only load the last saved puzzle.

Q17. I hit something and the numbers and pencil marks got so small that I can't see them. What happened?

You probably inadvertently changed the font size in your browser. Take a look in the "view" menu for the "font size" or "text size" option. Reset this to "normal", or larger if you want to. In some browsers, and 0 accomplishes the same thing.

Q18. Can you help me with the puzzle in my paper?

Use the Draw/Play function to input a puzzle from any source. The page will allow you to validate the puzzle for a single solution, logic-only answer, get hints, and check the solution.

Q19. The "Play online" function suddenly stopped working. What happened?

You may have accidentally disabled javascript in your browser. Check this page for a description of how to reenable it.

Your internet browser (most likely Internet Explorer) may have automatically updated, disabling javascript or changing some other setting. (Hopefully the people at Microsoft haven't actually broken anything!) Check your settings as above, and email us with your operating system and browser version if you still have a problem. For your info, we find that Firefox "just works" more often than anything else. Give it a go if you want to try something other than IE.

Please note, the "Play online" pages just won't work in IE on a Mac, or in Safari on a pre OS X Mac.

Q20. Can I get more?

Daily Sudoku Books, by Sam Griffiths-Jones, are available in many countries, but are currently out of print in the UK.

We have also published several E-books, each with 40 unique and graded puzzles, available for only 2, for those times when you're no where near a computer. Go to the books page for more information.

Q21. I run a website/newspaper/magazine that would like to include your Sudoku puzzles.

There are several options for syndicating Daily Sudoku puzzles. See the syndication page for more information. It is important to note that all our puzzles are copyrighted.

Q22. I love your site and I want to donate some money to help you keep it going!

The Daily Sudoku aims to be free for ever. However, there are some costs associated with running the site. The best way to help us keep it going is to buy an E-book.