MP3 to M4B audiobook converter
Apple Books only gives audiobook features — resume where you left off, sleep timer, speed controls — to .m4b files, and there's no built-in way to make one. Drop an MP3 and get a proper M4B, encoded at spoken-word-friendly bitrates.
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M4B is AAC audio in an MP4 container with one meaningful difference: the extension tells audiobook apps to treat the file as a book. Apple Books remembers your playback position per file, offers speed controls and a sleep timer, and shelves it with your audiobooks — none of which happens if the same audio arrives as an MP3 or M4A, which get treated as music and restart from zero. Apple provides no built-in way to make an M4B, which is why narrators, students, and self-audiobook listeners end up hunting for a converter.
This one runs in your browser: the audio is re-encoded to AAC at spoken-word bitrates (64 kbps is transparent for voice) and wrapped in the iPod-flavored MP4 container Apple Books expects. Nothing uploads — a multi-hour recording converts locally at native speed. Drop in a lecture recording, a narrated draft of your own writing, or a long-form generated narration, and get a file that behaves like a real audiobook on iPhone, iPad, and Mac.
How it works
- 1
Drop the MP3 (or M4A/WAV) recording.
- 2
Pick a quality — 64 kbps is the audiobook standard.
- 3
Download the .m4b and add it to Apple Books (drag into the app, or share to Books on iPhone).
When to use it
- Convert a recorded lecture or sermon series into an M4B so Apple Books resumes exactly where you stopped.
- Turn a narrated draft of your own book into an audiobook file you can test-listen to like the real thing.
- Repackage long-form AI-generated narration as an audiobook with proper speed and sleep-timer controls.
FAQ
Why M4B instead of just MP3?
The .m4b extension is what tells Apple Books (and many audiobook apps) to treat the file as an audiobook rather than music: playback position is remembered per book, and you get audiobook controls like speed and sleep timer. The audio inside is standard AAC.
Can I combine many MP3s into one audiobook?
Join them first with the gapless combiner, then convert the single file here. Chapter markers aren't written yet — the file plays as one continuous book.
How do I get the M4B into Apple Books?
On a Mac, drag the file into the Books app. On iPhone or iPad, save it to Files, then use the share sheet → Books (or open it from Files with Books installed). It appears under Audiobooks.
What bitrate should I pick for an audiobook?
64 kbps AAC is the industry standard for spoken word — commercial audiobooks ship at or below it. Choose 96 or 128 only if the recording has significant music or you're archiving a high-quality narration master.
Does it support chapters?
Not yet — the output plays as one continuous book with position memory. If you're combining multiple MP3s, join them with the gapless combiner first, then convert the single file here.
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