Guide · KDP rules

Copyright and trademarks in puzzle books

Most puzzle publishers never have a legal problem, and the ones who do usually hit one of five things: a puzzle name, a brand in a word list, a font licence, a borrowed puzzle or a misleading title. Here is what we found when we checked, and what to check yourself.

Updated 29 October 2026 · Examples are real, unedited pages from the Gridbinder studio unless the caption says otherwise.

Puzzle names

Many puzzle types were named by the Japanese publisher Nikoli, and some of those names are trademarks in Japan. Nikoli itself states that Sudoku is its registered trademark in Japan; in the US the word is widely used to describe the puzzle. In October 2026 we searched public trademark listings (through search engines, not a direct registry query) and found:

  • Nurikabe and Kakuro: US applications by Nikoli that were abandoned; Kakuro also appears in some software trademarks.
  • Killer Sudoku: a US application from 2024 for game software, status not settled when we looked; an older EU application was refused.
  • Slitherlink: no US record found; a third party states it is registered by Nikoli in Japan.
  • Masyu, Star Battle, Anti-Knight Sudoku: no record found.
  • Numberlink: no record for the puzzle found. Gridbinder calls it Number Paths anyway, a plain descriptive name.
  • Word Search Puzzles (the full phrase) is a registered US mark for a book series; "word search" is used everywhere as the name of the puzzle.

Not finding a record is not proof that none exists. If you sell in Japan or are unsure, check the registry (in the US, the USPTO's trademark search) or ask a lawyer before printing a name in a title. Using a descriptive phrase such as "number crossword" next to the name in your description is a common precaution.

Brand names in word lists and titles

A word search about breakfast cereals, cars or a TV show tempts you to use brand names. KDP Community threads on word search lists and brand names show publishers being careful here, and KDP's guidelines do not allow metadata that misleads customers. Use generic words ("cereal", "pickup truck"), and keep other brands, famous names and other books' titles out of your title, subtitle and keywords.

Fonts

A font is software with its own licence. Fonts under the SIL Open Font License (OFL), such as Atkinson Hyperlegible, which Gridbinder uses, may be embedded in PDFs and used in commercial books. Fonts that came with your computer or a design app may not allow that; read the licence. KDP requires all fonts to be embedded in the PDF.

Your puzzle source and your copyright page

  • Keep the licence or terms of whatever made your puzzles, with the date. If KDP ever asks where content comes from, that is your evidence.
  • Whether software-generated puzzles are protected by copyright is not settled and differs by country. Rely on the licence, not on owning the puzzles.
  • Write your own copyright page: your name or imprint, the year, and a short rights statement. Gridbinder fills in a default you can edit.
A copyright page from a 6 x 9 inch puzzle book with a short notice at the bottom of the page
The copyright page of a 6 x 9 in book made in the studio, with the default text. You can change it before you make the book.

Questions

Can I use the word Sudoku in my book title?

In the US it is widely used to describe the puzzle, and many books do. Nikoli states it is a registered trademark in Japan, so take care when selling there. This is not legal advice.

Do Sudoku books need to be copyrighted?

You do not need to register anything to publish. Add your own copyright notice, and keep the licence that allows you to sell the puzzles.

Can I use brand names in a word search?

It is safer to use generic words. Brand names are trademarks, and misleading use in metadata can get a book rejected.

Sources

KDP changes its rules from time to time. If a number here and the KDP help page disagree, the KDP page wins; please tell us at support@arling.sk.