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MOBI (Kindle ebook)

MOBI is an ebook format originally from Mobipocket that Amazon adopted for early Kindle devices. It holds reflowable book text with chapters and basic formatting, but Amazon has retired it in favor of newer Kindle formats and no longer accepts MOBI uploads.

Files & formatsGeneral

MOBI (Kindle ebook)

Also known as: .mobi file, Mobipocket, Kindle book format

MOBI is an ebook format originally from Mobipocket that Amazon adopted for early Kindle devices. It holds reflowable book text with chapters and basic formatting, but Amazon has retired it in favor of newer Kindle formats and no longer accepts MOBI uploads.

  • Early Kindle ebook format from Mobipocket
  • Reflowable text, unlike fixed-page PDF
  • Amazon retired it; convert to EPUB for current readers

What MOBI is

MOBI is a reflowable ebook format — text adapts to the screen and font size rather than staying on fixed pages like a PDF. Amazon built its early Kindle ecosystem on MOBI and the related AZW formats.

Amazon has since moved Kindle to KFX and recommends EPUB for new content. As of 2022, the Send to Kindle service stopped accepting MOBI files, though existing MOBI books still open in many readers.

Opening and converting MOBI

Apps like Calibre, plus various ebook readers, open MOBI files. To use one on a current Kindle or other reader, convert it to EPUB, the widely supported open ebook standard.

MOBI files are small — mostly compressed text — so they take little storage. Books with many embedded images are the larger exception.

Related terms

Keep reading the reference.

Files & formatsAZW3 (Kindle)AZW3, also called Kindle Format 8 (KF8), is Amazon’s ebook format that succeeded MOBI on Kindle devices. It supports richer formatting and layout than MOBI and may carry Amazon DRM that ties a book to your Kindle account.GeneralFiles & formatsEPUBEPUB is the open standard format for ebooks. It is a ZIP package of HTML, CSS, and images, and its text reflows to fit any screen size — unlike a PDF, which keeps a fixed page layout. Most e-readers except Amazon Kindle support it natively.GeneralFiles & formatsPDFPDF (Portable Document Format) is a fixed-layout document format that looks the same on any device. Most PDFs are small, but scanned documents and image-heavy files can grow large, and they accumulate quietly in Downloads and the Files app.GeneralFiles & formatsPlain text (.txt)A plain-text file (`.txt`) contains only unformatted text — characters with no fonts, colors, images, or layout. It is the simplest, most universal document format, readable by virtually any device or program.General