FormatDrop
Document Format

EPUB

Electronic Publication

EPUB is the open-standard ebook format used by Apple Books, Kobo, Google Play Books, and most non-Kindle ereaders. It wraps HTML, CSS, and images into a single file that reflows to fit any screen size. It is the ebook equivalent of HTML — adaptable, open, and widely supported, except on Kindle.

What is EPUB?

EPUB (Electronic Publication) is an open standard maintained by the W3C (World Wide Web Consortium), with the current EPUB 3 specification released in 2011 and updated since. Internally, an EPUB file is a ZIP archive containing XHTML/HTML5 content files, a CSS stylesheet, metadata (in XML), images, fonts, and a navigation document. This structure is essentially a self-contained mini-website. Because EPUB is based on HTML, text reflows dynamically to fit the screen — a key advantage over PDF, where layout is fixed. EPUB 3 supports JavaScript (for interactive features), audio and video embeds, MathML for mathematical notation, and comprehensive accessibility features. EPUB is the default format for virtually all ebook stores except Amazon: Apple Books, Kobo, Barnes & Noble Nook, and Google Play Books all use EPUB natively. The EPUB specification is maintained by the W3C, ensuring it remains open and royalty-free.

EPUB pros and cons

Advantages

  • Text reflows to fit any screen size and font preference
  • Open standard — no vendor lock-in
  • Supported by Apple Books, Kobo, Google Books, and most ereaders
  • Supports embedded fonts, images, audio, and video (EPUB 3)
  • Accessible — screen readers work well with EPUB
  • Adjustable font size and reading settings

Limitations

  • Not natively supported by Kindle (uses MOBI/AZW/KFX formats)
  • PDF readers and word processors generally cannot open EPUB
  • Windows does not include an EPUB reader by default
  • Fixed-layout books (comics, textbooks) don't always render perfectly
  • Less predictable layout control than PDF

When should you convert EPUB files?

Convert EPUB to PDF when you need a fixed-layout document — for printing, formal submissions, sharing with people who don't have an ebook reader, or viewing on devices and software that only support PDF. PDF preserves the exact layout of every page. Convert PDF to EPUB when you want to read a PDF as a proper ebook — the conversion will attempt to reflow text into a readable EPUB, though complex PDFs with multi-column layouts or heavy graphics may not convert cleanly.

Convert EPUB files

EPUB→PDF
PDF→EPUB

All FormatDrop conversions run entirely in your browser — no file upload, no server processing. Your files stay on your device.

EPUB FAQ

Can I open EPUB on Kindle?
Not directly — Kindle devices use Amazon's proprietary AZW/MOBI/KFX formats. However, Amazon's Kindle app for iOS and Android added limited EPUB support in 2022. On older Kindles or Kindle e-readers, you would need to convert EPUB to MOBI using a tool like Calibre, then transfer via USB or Send-to-Kindle. The most universal approach for sharing ebooks across devices is PDF.
What's the difference between EPUB and PDF?
The fundamental difference is layout. PDF is a fixed-format document — every page looks exactly the same regardless of screen size, font settings, or device. EPUB is a reflowable format — text wraps dynamically based on screen size and the reader's font preferences. This makes EPUB much better for long-form reading on small screens, but PDF better for documents where exact layout matters (forms, manuals, print-ready files). For novels and text-heavy books, EPUB provides a better reading experience. For illustrated books, textbooks, or documents that need precise formatting, PDF is more reliable.
How do I open an EPUB file on Windows?
Windows doesn't include an EPUB reader by default. Options include: (1) Microsoft Edge (version 93+) — click the EPUB file and Edge should open it directly, (2) Calibre — a free, open-source ebook manager that opens EPUB files, (3) the Kindle app with EPUB support, or (4) convert the EPUB to PDF using FormatDrop and open it in any PDF viewer.

More formats

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