EPUB 2 and EPUB 3 cannot be distinguished by the .epub extension alone. The useful differences involve the primary navigation mechanism, the generation of web technologies used for content, metadata conventions, and the reading systems a publisher must support. The Rune Studio evidence available here covers EPUB 3 only.
Navigation moved to a different center
EPUB 2 commonly relies on NCX as its primary navigation resource. EPUB 3 uses an XHTML EPUB Navigation Document, often named nav.xhtml. An EPUB 3 package may also include NCX for compatibility with older systems, but the presence of NCX does not turn it into EPUB 2.
A contents page visible inside the book is another distinct concept. Visible contents, reading-system navigation, and default reading order can correspond without being the same resource. The EPUB 3.3 Recommendation provides the current EPUB 3 standard reference.
Content technology and metadata changed as well
EPUB 3 is built on a newer HTML and CSS foundation and expanded support for areas such as media and accessibility. Renaming an EPUB 2 package does not convert its content or package rules. A publisher must identify the standard version and then check whether required features are supported by the target readers.
EPUB 3 capability also does not mean every reading app implements every feature. Format selection and device support are two different decisions.
What Rune Studio's EPUB 3 output showed
Rune Studio's six-page wizard creates EPUB 3 from publication information, volume choice, selected manuscripts, chapter order, metadata, and the final review. Its documented output includes nav.xhtml, a compatibility NCX, and metadata, manifest, and spine information in content.opf.
In a three-chapter inspection, nav contained three chapter destinations, NCX contained three navigation points, and the six-item spine ran through title, navigation, three chapters, and colophon. Series and volume values were present, and the local structural check was valid. Those are observations from an EPUB 3 specimen.
Do not turn a missing comparison into a result
The current Rune Studio workflow does not provide an EPUB 2 export option. The planned same-source generation of EPUB 2 and EPUB 3 was therefore blocked. It would be inaccurate to claim that the application proved a conversion difference or generated both formats.
A real package comparison needs a trustworthy EPUB 2 specimen with known provenance. Inspect its package version, NCX, content documents, and reading order using the same questions applied to the EPUB 3 artifact. An unidentified old ebook is a poor standards reference.
Choose from the delivery requirement
For new production, EPUB 3 is the default candidate when the destination supports it. A requirement for an older device or existing EPUB 2 asset needs separate compatibility testing and possibly another tool. Rune Studio is relevant to EPUB 3 creation; it does not answer a requirement for native EPUB 2 export. Check the application's current scope before selecting it for the job.
