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What is an EPUB file?
An EPUB file is a digital book (eBook) saved in the open Electronic Publication (EPUB) format, a standard digital publication format that publishers and consumers use to distribute eBooks. Many users encounter EPUB files when downloading eBooks (such as books, magazines, scientific publications, etc.). You can open an EPUB file with eReader apps, such as Calibre and Apple Books, and devices.
The International Digital Publishing Forum (IDPF) initially released the EPUB format in 2007 as a replacement for the Open eBook (OEB) format. EPUB has undergone several revisions since its release, with its most recent version, 3.3, released in May 2023.
The EPUB format is Zip-based and stores resources that make up the publication, including .XML, .XHTML, .NCX, .CSS, and .SVG files. These files contain the publication's contents, including its text, chapter links, cover art, and images. Many commercial eBooks also include digital rights management (DRM) protection, which limits viewing to only authorized devices.
How to open an EPUB file
You can also edit EPUB files with no DRM protection with several apps. One of the most common eBook editors is Calibre.
Opening an EPUB file as a Zip archive
Since EPUB files store their contents in a Zip-like container format, you can open them with Zip compression utilities. For example, you can open an EPUB file as a Zip archive with Windows File Explorer by renaming the .epub file extension to .zip. You can then extract its contents to view or modify them. However, remember that editing the contents in an EPUB file may corrupt the eBook.
How to convert an EPUB file
Calibre can convert EPUB files to various file types, including the following formats: