Media type / application
application/epub+zip
EPUB electronic books: a ZIP container of XHTML content, navigation, and assets.
Served inline: Browsers have no renderer for this, so it downloads even without a Content-Disposition header. That makes it the quiet default for anything you do not want opened in place.
Browser behaviour
Downloads
Charset
no charset
Compression
Already compressed
Send it like this
Content-Type: application/epub+zipA binary payload has no character encoding. A charset parameter here is meaningless and occasionally confuses strict parsers.
Handling verdict
Browsers have no renderer for this, so it downloads even without a Content-Disposition header. That makes it the quiet default for anything you do not want opened in place.
A binary payload has no character encoding. A charset parameter here is meaningless and occasionally confuses strict parsers.
The format compresses internally. Another transport encoding costs CPU on both ends and typically changes the size by less than a percent — sometimes upward.
Registered with IANA through a public review process, so the name is stable and every implementation can rely on it meaning the same thing.
Anatomy of the name
RFC 6838Top-level type
application
Application
Subtype
epub+zip
Registered in the standards tree.
Structured syntax
+zip
The payload is a ZIP archive, so its bytes begin with the ZIP signature and generic unzip tools can open it.
Parameters
none
Beyond the charset rule above, this type defines no parameters of its own.
Response headers
Content-Type: application/epub+zip
X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename="example.epub"nosniff stops the browser second-guessing the type you declared, which is what makes the rest of this reliable. Content-Disposition: attachment names the saved file and removes any doubt about rendering.
Server configuration
extension mappingnginx
types {
application/epub+zip epub;
}Apache
AddType application/epub+zip .epubCaddy
@type path *.epub
header @type Content-Type "application/epub+zip"Extensions and other spellings
with signatureFile extensions
File signature
50 4B 03 04
Check these bytes rather than the client-supplied Content-Type when validating an upload. The header is a claim; the signature is evidence.