M4B to MP3. For car stereos, old MP3 players, and Android.
Audiobooks ship as .m4b — AAC audio in an MP4 wrapper with chapter markers. Great inside Apple Books. Useless in a 2012 Honda's CD-stick port. Drop your DRM-free M4B here, get an MP3, plays everywhere. No iTunes, no Audacity, no upload.
drop your M4B audiobook
Librivox, Apple Books (DRM-free), indie author files. Batch supported.
What this works on (and what it doesn't)
Works:
- Librivox audiobook downloads (public domain, always DRM-free)
- Apple Books / iBooks free public domain titles
- Indie author M4B releases sold directly
- Audiobooks you ripped from your own CDs and encoded as M4B
- Podcast bundles distributed as a single M4B with chapters
Doesn't work:
- Audible files (.aax, encrypted .m4b) — these have DRM and we don't break DRM
- Apple Books titles you bought that are still DRM-locked
- Anything with FairPlay encryption
If the file opens in VLC or QuickTime without entering a password, it's DRM-free and we can convert it.
Why split chapters separately
M4B chapter markers translate poorly to MP3. Players ignore them. The reliable workflow:
- Convert M4B → MP3 here (single big file).
- Note the chapter timestamps (visible in iTunes/Apple Books or in any M4B reader).
- Use our audio cutter to slice at those timestamps.
- You now have Chapter 01.mp3, Chapter 02.mp3, etc. — playable on anything.
This also makes it easy to load into a podcast player like Pocket Casts or AntennaPod as a custom feed.
Bitrate guidance for spoken word
- 64 kbps — fine for voice, half the size of 128. Use for 20+ hour books where storage matters.
- 96 kbps — sweet spot for narration. Clean S sounds, no warble.
- 128 kbps — default. Indistinguishable from source for voice.
- 192+ kbps — overkill for audiobooks. Save it for music.
FAQ
What's an M4B file?
It's an MP4 container holding AAC audio plus audiobook metadata (chapters, bookmark position, cover art). Same codec as M4A — just a different file extension that signals "this is a book, remember my place."
Will this work for Audible books?
No. Audible uses .aax with DRM, and even .m4b downloads from Audible are encrypted with your account key. You'd need Audible's own apps or a separate tool that handles their authorization. This tool only converts unencrypted M4B.
Why does my car stereo see "no files" when I copy an M4B?
Older head units only scan for .mp3 (sometimes .wma). They literally ignore .m4b files even though the audio inside is fine. Converting to MP3 fixes it.
Will I lose chapter markers?
The MP3 won't have native chapter markers your player recognizes. The audio is fine. If you need chapters as separate files, convert to one MP3, then split using our audio cutter.
Is the conversion lossy?
Both M4B (AAC) and MP3 are lossy, so this is a re-encode. At 128+ kbps for spoken word, the loss is inaudible. For music inside an M4B (rare), pick 192 kbps to be safe.
How long will a 12-hour audiobook take?
Roughly 4–8 minutes on a modern laptop. We're decoding the AAC and re-encoding as MP3 — both fast in WebAssembly, but it's still 12 hours of audio.
Does anything leave my computer?
No. Conversion happens in your browser tab. Try airplane mode.