EPUB

An open ebook format packaging XHTML, CSS and images in a ZIP, with text that reflows to the reader's screen and font size.

Representation

binary

Compression

Deflate

Lossy

No

Open specification

Yes

Encryption support

Yes

Introduced

2007

Organisation

IDPF, now W3C

• Windowspartial
• macOSfull
• Androidfull
• iOSfull

Applications: Apple Books, Kobo, Calibre, Google Play Books.

• Reflows to any screen size
• Adjustable fonts and accessibility support
• Open standard

• Not supported by Kindle's older formats
• Fixed layouts (comics, textbooks) render inconsistently

• Novels and long-form reading
• Library lending
• Self-publishing

EPUB to PDF fixes the layout and loses reflow, which is a downgrade for e-reader use.

• EPUB to PDF
• EPUB to MOBI
• EPUB to AZW3
• EPUB to HTML
• EPUB to TXT

Every conclusion below is derived from the structured facts on this page — nothing is written by hand.

• Operating system compatibility100/100

  • Because Windows, macOS, Linux, Android and iOS all open it without extra software.
  • Because most platforms handle it natively.

• Software compatibility100/100

  • Because a broad range of applications read and write it.
  • Because several mainstream applications support it.

• Cloud compatibility100/100

  • Because an open specification means cloud SDKs can implement it without licensing friction.
  • Because it converts into many other formats, which suits automated pipelines.

• AI compatibility100/100

  • Because open specifications are implemented by the open-source decoders that ML stacks rely on.
  • Because lossless pixels avoid compression artefacts leaking into training data.
  • Because wide library support means common data loaders can read it.

• Long-term archiving100/100

  • Because the specification is public, so a decoder can always be rebuilt.
  • Because lossless storage preserves the original data for future migrations.
  • Because it is a current, actively maintained format.

• Professional editing100/100

  • Because lossless data survives repeated open-edit-save cycles without degrading.
  • Because professional applications read and write it.

• Open standards100/100

  • Because the specification is published openly.
  • Because an official specification document is publicly reachable.

• Popularity100/100

  • Because it sits at the centre of the format ecosystem, with many documented relationships.
  • Because mainstream applications ship support for it.
  • Because every mainstream operating system handles it.

• Future-proofing100/100

  • Because it is actively maintained and current.
  • Because open specifications outlive the companies that create them.
  • Because nothing in the graph supersedes it yet.

• Everyday consumer usage75/100

  • Because it opens by double-clicking on every mainstream device.
  • Because it is a current format that people and services still expect.

• Printing suitability71/100

  • Because lossless data means no compression artefacts appear at print resolution.

• Compression efficiency23/100

  • Because it stores data losslessly, so files stay large.
  • Because its codec generation predates modern entropy coding and block partitioning.

• Web suitability33/100

  • Because lossless payloads cost more bandwidth than the web usually justifies.