An EPUB e-book — a ZIP archive containing XHTML content and a manifest.
| 0x00000000 | 504B0304 | PK·· | 'PK' — it is a ZIP |
Inside the ZIP: a 'mimetype' entry whose contents are 'application/epub+zip'.
EPUB is the open e-book standard: a ZIP of reflowable XHTML, CSS and images that adapts to any screen size. It is recognized by an uncompressed 'mimetype' entry stored first in the ZIP.
Have a file that might be EPUB? Identify it with the File Type Identifier — it reads the magic number locally, nothing is uploaded. Or browse all formats.