Get MP3 audiobooks into Apple Books

Apple Books wants an audiobook as one .m4b file: that's where it gets the chapter list, the cover in the library and the remembered position. Kataribe turns a folder of MP3s into exactly that, in your browser, ready to import on your Mac and sync to your iPhone.

If you ripped audiobook CDs into iTunes years ago, you know the failure mode: one book shows up as 90 tracks, the chapter menu is empty, and stopping halfway through track 47 means finding track 47 again tomorrow. Drop the tracks here. The ID3 tags fill in title, author and cover, the track numbers set the order, every track becomes a chapter, and titles like "Track 07" can be renamed or left alone. At 64 kbps AAC, a 12-hour book comes out around 350 MB.

Then File → Import in Books on the Mac, or drag the .m4b into the Audiobooks section, and sync to the iPhone; steps for both are below. Books shows the chapter list, remembers where you stopped, and keeps the book out of your music. Nothing is uploaded on the way: the conversion runs on your machine.

After you download the .m4b

Apple Books

  1. Mac: drag the .m4b into Books, or File → Add to Library. It lands under Audiobooks with the cover and chapters.
  2. iPhone / iPad: connect the device and sync audiobooks in Finder (or iTunes on Windows), or AirDrop the file and open it in Books.
  3. Books remembers your position and shows the chapter list from the file — that's the whole point of M4B over a folder of MP3s.

Frequently asked questions

Can't I just import the MP3s into Books directly?
You can, and Books will list them, but as separate tracks: no chapter list, no single entry in the library, and your place isn't reliably kept. One M4B is one book, with chapters and a position Books remembers.
How do I get the M4B onto my iPhone?
Import it into Books on the Mac, connect the iPhone, and sync audiobooks from the Finder sidebar. Or AirDrop the .m4b to the phone and choose Books when asked. Either way it appears under Audiobooks with its cover and chapters.
Why didn't iTunes' Create AAC Version give me chapters?
It converts one track into one M4A and writes music tags; it never joins files or writes chapter markers. Kataribe does both, and can take those M4As as input without re-encoding them.
Does Books show the cover and narrator?
The cover shows in the library and the title and author are what Books lists. Narrator, year and the Audiobook genre are written into the file's metadata, so other players that display them will.
Are my audio files uploaded anywhere?
No. Kataribe runs FFmpeg compiled to WebAssembly inside your browser, so the files never leave your device. The engine (about 30 MB) downloads once and is cached; after that there is no account, no queue and no watermark.
How long does a full book take?
Encoding runs many times faster than real time on a modern laptop, but a full-length book still takes minutes, not seconds. Keep the tab open until the download appears. If every input is already AAC, the audio is copied rather than re-encoded, which is much quicker.
Is this really free?
Yes. Every input format, every bitrate, cover art and metadata, no sign-up, and nothing added to the audio.
Does it work with DRM-protected audiobooks?
No. DRM-protected files (Audible .aax and similar) won't open, and we don't help with that. Kataribe is for audio you already have in plain MP3, M4A, WAV, FLAC or OGG.