EPUBCheck
The official validation tool that confirms an EPUB meets the standard. Passing it is what gets a book accepted by stores.
More in Ebook & digital
Alt text
A written description of an image, read aloud by assistive technology — essential for accessible ebooks.
DRM
Digital Rights Management — copy protection applied to ebooks. Optional, and a choice with trade-offs for readers.
EPUB
The open standard ebook format read by Kobo, Apple Books, Nook, Google Play and most readers. EPUB 3 is the current version.
Fixed-layout
An ebook that keeps an exact page design, like a PDF — used for children's books, cookbooks and heavily designed pages.
Metadata
The data describing a book — title, author, ISBN, description, keywords, categories. Good metadata is how readers find you.
MOBI / KF8
Older Kindle formats. Amazon now prefers EPUB and converts it internally; standalone MOBI is effectively retired.