MOBI File Format (.mobi)

A MOBI file holds an ebook in Mobipocket's format, a text document compressed and stored inside a Palm Database (PDB) container that Amazon adopted for the original Kindle.

.mobiDocuments

MOBI at a glance#

Full name	Mobipocket ebook
File extension	.mobi
Category	Documents
Developer	Mobipocket
First released	2000
MIME types	application/x-mobipocket-ebook
Other extensions	.prc
Compression	Lossless
FileFlip support	FileFlip reads this format but does not write it

What a .mobi file can hold#

These are the things a MOBI file either supports or does not, and they are what decides whether a conversion keeps everything or quietly drops something.

Embedded metadata	Yes
Multiple images or pages	Yes
Selectable text	Yes
Chapters	Yes
Encryption	Yes

Strengths and limitations of MOBI#

What MOBI does well

Compresses body text with PalmDOC's LZ77 scheme, so books stay small on early low-memory Kindles
Every Kindle device and app made before the 2022 cutover reads it without conversion
Widely supported by legacy ebook tools like Calibre and older Mobipocket Reader installs

Where MOBI falls short

Amazon stopped accepting MOBI for Send to Kindle and Kindle publishing in 2022, converting incoming files to KFX instead
Its Palm-era layout engine has no equivalent to EPUB 3's fixed layout, embedded audio or video
Files locked with Mobipocket or Amazon DRM cannot be opened or converted without the original registration

There is little reason to create a new MOBI file today; it matters only for reading an ebook already saved in the format.

Convert MOBI to EPUB or PDF because Amazon no longer accepts MOBI directly and current Kindle software expects KFX or EPUB instead.

How to open a .mobi file#

A .mobi file opens in the programs below, grouped by the platform you are on. If you would rather not install anything, FileFlip converts MOBI into a format your machine already opens, and it does it in the browser tab rather than on a server.

Platform	Programs that open it
Windows	Calibre, SumatraPDF
macOS	Calibre
Linux	Calibre, Okular, FBReader
Web	FileFlip

MOBI questions people ask#

What is a MOBI file?

A MOBI file is an ebook in the format Mobipocket built on top of the Palm Database (PDB) container, the same file structure Palm OS devices used for their own databases. Amazon acquired Mobipocket in 2005 and used the format for the first decade of Kindle devices.

Why won't my MOBI file work on my Kindle anymore?

Amazon announced in April 2022 that it would stop accepting MOBI files through Send to Kindle and Kindle Direct Publishing by the end of that year, converting uploads to KFX or the EPUB-derived AZW3 format instead. A MOBI file made before that change often still opens on an older Kindle, but current Kindle software and newer devices expect the file already converted.

What replaced the MOBI format?

KFX, Amazon's current Kindle format, replaced MOBI, along with AZW3 (Kindle Format 8) which Amazon introduced back in 2011. Both handle layout and typography that the older MOBI format cannot, and Amazon now converts incoming EPUB files to KFX rather than accepting MOBI as an input.

Can I remove DRM from a MOBI file to convert it?

No converter can remove DRM from a MOBI file. Mobipocket and Amazon both used encryption schemes tied to a device or account registration, and a protected MOBI file will fail to convert rather than produce readable output.

Converting MOBI files#

FileFlip does not write .mobi files, so nothing on the site converts into this format. It works as a source only.

Every conversion runs inside your browser. The file is read from your disk, the work happens on your own machine, and nothing is uploaded. How FileFlip works names the engine behind each family and how to verify that for yourself.