The short answer
- EPUB is a digital-publication document format that packages structured web content into one ZIP-based OCF container, with a package document defining its resources and default reading order.
- Open the .epub file with an EPUB-conforming reading system. If it fails, confirm the extension and MIME type, then check that the ZIP-based container begins with the required uncompressed mimetype entry and contains META-INF/container.xml.
- Treat an EPUB from an unknown source as potentially active web content. It can contain JavaScript, remote resources and links; use an updated reading system with appropriate script and network restrictions, and remember that an optional digital signature is not a guarantee against tampering.
EPUB Publication File
An EPUB publication can contain XHTML, CSS, SVG, images and other resources. Its package document provides metadata, a manifest and a spine, and may declare reflowable or fixed-layout presentation.
Choose a destination format according to what must be preserved. Fixed or less capable formats can lose reflow, scripts, media overlays, audio, video, semantic metadata or navigation, so compare the converted output with the source EPUB.
How to open it
Open the .epub file with an EPUB-conforming reading system. If it fails, confirm the extension and MIME type, then check that the ZIP-based container begins with the required uncompressed mimetype entry and contains META-INF/container.xml.
Open the .epub file with an EPUB-conforming reading system. If it fails, confirm the extension and MIME type, then check that the ZIP-based container begins with the required uncompressed mimetype entry and contains META-INF/container.xml.
Choose a destination format according to what must be preserved. Fixed or less capable formats can lose reflow, scripts, media overlays, audio, video, semantic metadata or navigation, so compare the converted output with the source EPUB.
File safety
Treat an EPUB from an unknown source as potentially active web content. It can contain JavaScript, remote resources and links; use an updated reading system with appropriate script and network restrictions, and remember that an optional digital signature is not a guarantee against tampering.
An unknown sender, a name ending in two extensions, or contents that do not match the extension — check before you open it.
Converting it
Choose a destination format according to what must be preserved. Fixed or less capable formats can lose reflow, scripts, media overlays, audio, video, semantic metadata or navigation, so compare the converted output with the source EPUB.
Convert a copy, never the original, then compare quality, metadata, and layout against what you started with.
Common questions
What is an EPUB file and what is it used for?
An EPUB file is a distribution and interchange format for digital publications. It packages structured web content such as XHTML, CSS, SVG, images and other resources into a single file.
How do I open an EPUB file?
Use an EPUB-conforming reading system and open the .epub file through that system. The reader processes the OCF container, package document, content documents and resources.
How do I open an EPUB file on Windows?
Choose a Windows reading system that supports EPUB, then open or import the .epub file. Interactive features may vary because scripting can be restricted or disabled.
How do I open an EPUB file on a Mac?
Use an EPUB-capable reading system on macOS and open or import the file. If its layout or interaction differs elsewhere, compare it in another conforming reader because feature support varies.
How do I open an EPUB file on a phone?
Open or import the file with an EPUB-capable mobile reading system. Network or script restrictions may affect remote content and interactive behavior.
Why will an EPUB file not open or appear corrupted?
The ZIP-based OCF container may be malformed, its mimetype entry may not be first and uncompressed, META-INF/container.xml may be missing, or declared resources may be unavailable. A damaged or excessively expanding archive can also be rejected.
Should I use EPUB or PDF for a digital publication?
Use EPUB when reflowable reading and EPUB navigation or media features matter. A fixed format may suit a fixed presentation, but conversion can discard EPUB-specific structure and behavior.
What can be lost when I convert EPUB to PDF?
Conversion to a fixed or less capable format can lose text reflow, scripted interaction, media overlays, embedded audio or video, semantic metadata and navigation. Check the result against the source.
Is an EPUB file safe to open?
Not automatically. EPUB can contain JavaScript, remote resources and links, while malformed ZIP data can target vulnerable parsers. Open untrusted files in an updated reader with suitable script and network restrictions.
What are the EPUB MIME type and container requirements?
The registered MIME type is application/epub+zip. The root mimetype entry must be first, uncompressed and unencrypted and contain exactly that value; META-INF/container.xml points to the package document.
Related formats
Sources
EPUB 3.3 · W3C Recommendation and normative EPUB specification
EPUB 3 Overview · W3C Working Group Note
IANA Media Types Registry: application/epub+zip · IANA official media-type registry