FILE FORMAT GUIDE
EPUB Publication (.EPUB): Structure & Inspection
An EPUB file is a ZIP-based Open Container Format package for an electronic publication. It combines package metadata, reading order and publication resources.
Check supported header evidence locally. Identification is not file validation or a malware scan.
Analyze a file locallyQuick facts
- Extension
- .epub
- Format
- EPUB Publication
- Category
- document
- MIME type
- application/epub+zip
- Standard / developer
- W3C
- Open with
- EPUBCheck
What is EPUB?
A conforming EPUB puts an uncompressed mimetype entry first and stores application/epub+zip in it. The package can contain active or externally referenced content, so listing ZIP entries is not equivalent to safe rendering.
- Deliver a reflowable or fixed-layout electronic publication and its resources
How to open EPUB
This workflow inspects structure or metadata without rendering embedded content. It does not establish safety, authenticity, rights or visual fidelity.
EPUBCheckCommand-line tool or library
Run epubcheck book.epub to check the publication against supported EPUB rules. Treat a clean report as conformance evidence, not as a malware scan or rights clearance.
Technical details
- Signature
- 50 4B 03 04 at offset 0; mimetype at offset 30; application/epub+zip at offset 38
- Encoding
- Not applicable
- Container
- EPUB Open Container Format ZIP
- Compression
- Stored or Deflate ZIP entries
Things to check
- Container validity does not guarantee content accessibility, correct reading order or safe handling by every reading system.
Related formats
- Portable Document Format
PDF is commonly fixed-layout, while EPUB packages publication resources for reading-system workflows that may reflow.
- XML Paper Specification Document
XPS is a fixed-layout document package, while EPUB is a publication package designed for reading systems.
Sources & review
Fact review: 2026-09-19. Unknown fields are not inferred from the file extension.