M4B to MP3 Converter
Turn an Apple audiobook file into a single MP3 that plays on car stereos, Android phones and cheap MP3 players. Chapter markers survive the conversion, but the cover image does not, and the result is one MP3 per book, not one file per chapter.
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Why convert M4B to MP3
M4B is an MP4 container holding AAC audio, with the extension changed so Apple Books and iTunes treat it as a book: they remember your position and show a chapter list. The audio inside is ordinary AAC, so the obstacle is the container. Older car head units, Sony and SanDisk players and plenty of Android apps scan a card for .mp3 and ignore everything else.
This page runs the file through ffmpeg on our servers: the AAC stream is decoded and re-encoded with LAME at a requested 192 kbps CBR. Audiobooks are often mono and recorded at 22.05 or 24 kHz, and at those rates LAME settles at 160 kbps instead; mono stays mono. Rates up to 48 kHz are kept, and there is no bitrate or quality menu on the page.
Chapter markers are copied into the MP3 as ID3 chapter frames, so this route answers the "M4B to MP3 with chapters" question honestly: in testing, a two-chapter M4B came out with both chapters intact. Title, artist and album become ID3 tags. Lost are the embedded cover image, stripped from every output we produce, and anything Apple-specific such as your saved listening position. Re-encoding AAC to MP3 is lossy on top of lossy, and the MP3 will usually be bigger than the M4B you started with, because audiobook AAC is often encoded far below 160 kbps.
This is for people with an unprotected audiobook who want it on hardware that has never heard of Apple Books: a commute player, a kid's MP3 stick, a USB drive for the car, a Plex or Jellyfin library that indexes MP3 cleanly. It is not a way around DRM and will not help with Audible .aa or .aax purchases.
How to convert an M4B audiobook
- Check the file first: a protected iTunes audiobook or an Audible .aa or .aax file cannot be converted here. Only a plain, unprotected .m4b goes through.
- Check the size: the limit is 50 MB without an account, 100 MB signed in, 200 MB on Plus and 1 GB on Pro, so a ten-hour book may need splitting with a desktop tool first.
- Drop the .m4b onto the upload area, or pick several at once; each is converted on its own, one MP3 per book. Other sources that can become MP3, such as m4a, aac or wav, work here too.
- Start the conversion and leave the tab open. Most audiobook files finish in well under a minute after the upload completes. The server allows up to 30 minutes per file, but the page stops waiting sooner, so a long book can show "Processing timeout" while the job is still running: reload later, or tick "Email me when conversion is done" if you are signed in.
- Download the MP3. It keeps your original file name with the new extension. If your player shows no chapter list, the markers are still in the file; that app simply does not display them.
What this converter actually does
- Copies M4B chapter markers into the MP3 as ID3 chapters instead of flattening the book into an unmarked block.
- Writes title, artist and album through to ID3 tags so the book still sorts correctly in a library.
- Requests 192 kbps CBR MP3; mono narration stays mono and the sample rate is kept up to 48 kHz.
- Handles several files in one request, up to 10 without an account, each producing its own MP3 named after the original.
- Accepts audiobook-adjacent sources too: m4a, aac, ALAC inside m4a, caf, flac and wav.
- No install needed, and no account for files under 50 MB; conversion runs on our servers, not in your browser.
Frequently asked questions
Will the chapters survive the conversion to MP3?
Yes. The chapter table is written into the MP3 as ID3 chapter frames; a test file with two chapters came out with both. Whether you see them depends on the player: VLC, foobar2000 and several Android audiobook apps read ID3 chapters, while many car stereos ignore them.
Can you split the audiobook into one MP3 per chapter?
No. This converter produces one output file per input, with no trimming or splitting, so a one-file audiobook stays a one-file MP3 with markers inside. For separate per-chapter MP3s, split the book first with a desktop tool, then convert the pieces here.
Why does my M4B fail with a DRM message?
Audiobooks bought with copy protection cannot be decoded, and the converter says so rather than producing silence. Audible (.aa, .aax) and protected iTunes (.m4p) files are refused outright. We cannot remove protection; use a copy you are entitled to convert.
Can I choose the bitrate, or convert without losing quality?
There is no quality selector. MP3 output is fixed at 192 kbps CBR, which LAME lowers to 160 kbps for 16 to 24 kHz sources, and any MP3 re-encode of AAC is lossy rather than bit-for-bit identical. For narration the loss is not audible in practice, but expect the MP3 file to be larger than the M4B.
My audiobook is 400 MB. What are my options?
Per-file limits are 50 MB as a guest, 100 MB with a free account, 200 MB on Plus and 1 GB on Pro, so a 400 MB book needs a paid plan or a split into parts before upload. Above 1 GB, sign in and use the pay-once large-file option for audio, which emails the download link.
What happened to the cover image?
It is removed. Every picture stream is dropped during conversion, so the MP3 arrives without the artwork. Add it back afterwards with a tag editor such as Mp3tag or Kid3.
Is this better than converting with VLC or ffmpeg?
It is the same family of tools: we run ffmpeg server-side with fixed settings, while VLC and the ffmpeg command line run offline and let you set the bitrate yourself. Use this page when you want one book converted without installing anything.
What happens to my file after the conversion?
Your uploaded M4B is deleted as soon as the job finishes, and the MP3 stays on a private random download link for about four hours before it is deleted automatically. Files are processed on our servers, not in the browser. File names, sizes and outcomes are logged, and signed-in users get a conversion history entry.
The conversion failed with an ffmpeg error. Now what?
The errors we have seen on this page come from a partially downloaded or damaged container, where ffmpeg stops mid-stream with an "Invalid data" or filter error. Re-download or re-export the audiobook and try again. This converter always processes the whole file, so if one long book keeps failing, split it with a desktop tool first and convert the shorter, clean pieces here.