How to open MOBI and AZW3 files on iPhone and iPad

You have a folder of .mobi or .azw3 files, maybe from an old Kindle, a bundle of DRM-free books or an author's newsletter. On an iPhone, tapping one usually leads nowhere: Apple Books does not open them, and the Kindle app does not import files from the Files app. Here is what these formats are and how to read them.

MOBI, AZW3 and KFX

All three are Amazon's Kindle formats, from oldest to newest.

• MOBI is the original format, inherited from Mobipocket. It handles simple novels well and complex layouts badly.
• AZW3, also called KF8, replaced it around 2011. It supports better typography, embedded fonts and more of what EPUB can do.
• KFX is what the Kindle Store delivers today. It is meant for Kindle devices and apps only.

Amazon's Send to Kindle service stopped accepting MOBI files in 2022 and now asks for EPUB instead, which is one reason old MOBI collections end up looking for a new home.

DRM-free files versus Kindle Store purchases

The format matters less than whether the file is locked. Books bought in the Kindle Store carry DRM (digital rights management) and only open in Amazon's apps and devices. No other reader can open them, and you should keep reading those in the Kindle app.

DRM-free MOBI and AZW3 files are different. Humble Bundle, Smashwords, many independent authors and plenty of older archives offer them, and any app that understands the format can open them.

Opening them on iPhone and iPad

1. Put the files where the Files app can see them: iCloud Drive, a cloud folder, or a download in Safari.
2. Pick a reading app that opens MOBI and AZW3 directly. Apple Books does not, so check the app's list of formats before you install it.
3. In Files, touch and hold the book, tap Share, and choose that app. Some readers can also import a whole folder at once.

Converting with Calibre when you need to

If you want to use a reader that only takes EPUB, convert the files on a computer with Calibre, which is free:

1. Add the MOBI or AZW3 files to Calibre.
2. Select them and click Convert books.
3. Choose EPUB as the output format and start the conversion.

Simple novels convert cleanly. Books with tables, footnotes or unusual layouts sometimes lose a little formatting, so open a converted copy and check a few pages before deleting the original.

Which format to keep for the long term

For a collection you want to read for years, EPUB is the safest choice. It is an open standard, every serious reader supports it, and it is what Send to Kindle now prefers too. Keep your DRM-free MOBI and AZW3 originals as a backup, but if you convert, convert to EPUB.

Reading Kindle files in Glosa

Glosa opens DRM-free MOBI and AZW3 files directly, alongside EPUB, PDF, text, Markdown and HTML, so there is nothing to convert. Import a book or a whole folder from Files with + in the library. Books from the Kindle Store stay in the Kindle app, since their DRM only allows Amazon's apps.