M4B to M4A Converter

How to Convert M4B to M4A Online

1. Upload Your M4B File: Drag and drop or click "+ Add Files" to load M4B audiobooks from your computer. Batch upload is supported — convert an entire audiobook series, a multi-chapter podcast set, or a folder of M4B rips with the same settings in one pass.
2. Pick an Audio Codec: Default is AAC — the same codec used inside the M4B container, so a copy-style re-mux keeps audio bit-perfect. Switch to ALAC (Apple Lossless) if you want a lossless M4A, or pick from MP2, AC3, FLAC, Vorbis, Opus, AMR, Speex, WMA, or WavPack inside the M4A container if a downstream player needs it.
3. Tune Bitrate, Sample Rate, Channels, or Trim (Optional): Use the Audio Quality Preset dropdown (Lowest/Low/Medium/High/Highest), pick a Constant Bitrate from 8-320 kbps, set a Variable Bitrate range (e.g. 64K-80K for spoken word), drop the Audio Sample Rate from 48000Hz to 44100Hz/24000Hz/22050Hz/16000Hz/8000Hz, switch Audio Channel from Stereo to Mono for narration, or use Audio Trim with start time and duration to extract a single chapter.
4. Convert and Download: Click "Convert" and your M4A downloads in seconds. Files process in your browser session — no sign-up, no watermark, no upload to a third-party server.

Why Convert M4B to M4A?

M4B and M4A are the same MPEG-4 audio container with a different file extension. Apple uses .m4b to flag a file as an audiobook so iTunes, Apple Books, and the Music app remember playback position, surface chapter markers, and route the file to the audiobooks library instead of the music library. Renaming the extension is sometimes enough, but a real conversion strips the audiobook flag, removes chapter atoms that confuse non-Apple players, and lets you re-encode bitrate, sample rate, and channel layout in one pass.

• Play audiobooks in apps that ignore M4B — VLC, Plex, Sonos, most car stereos, and many Bluetooth speakers happily play M4A but skip or misidentify M4B. Converting lets a 40-hour audiobook show up alongside the rest of your music library on a Sonos or in Android Auto.
• Move audiobooks off Apple Books into a generic music app — Apple Books on iOS holds M4B files hostage in its own library. A converted M4A file imports cleanly into Spotify's local files, Plexamp, foobar2000, Poweramp, or any folder-based player that scans .m4a but ignores .m4b.
• Shrink long audiobooks for older iPhones and Android phones — A 12-hour audiobook ripped at 128kbps stereo AAC is around 660MB. Re-encoding to 64kbps mono during the M4B-to-M4A conversion brings it under 350MB while keeping speech perfectly intelligible — leaving room for the next 5 books on a 32GB device.
• Email or share short clips under attachment limits — Gmail and Outlook cap attachments at 25MB, Discord's free tier sits at 25MB (Nitro Basic 50MB). Trim a single 30-minute chapter out of an M4B and re-encode at 48kbps mono and the resulting M4A drops well under the limit.
• Use audiobook audio in editing tools — DAWs and video editors (Audacity, Logic Pro, Premiere, DaVinci Resolve) accept M4A AAC import directly but stumble on the audiobook chapter atoms inside M4B. Converting cleans the container so the file imports as a single timeline asset.
• Strip iTunes audiobook flagging from a self-made file — When you build an M4B with AudioBookConverter, abbinder, or mp4chaps, iTunes sometimes locks playback position even after deletion. Converting back to M4A resets the file to plain audio so it behaves predictably. See also Convert M4A to MP3 when you also need Android-friendly output.

M4B vs M4A — Format Comparison

M4A Bitrate Quick Guide for Converted Audiobooks

Frequently Asked Questions

Will my chapter markers survive the M4B to M4A conversion?

Standard M4B chapter atoms (the chpl and Nero-style chapter tracks written by AudioBookConverter, abbinder, and mp4chaps) are preserved when you choose AAC and skip a re-encode. If you change codec or trim, the chapter offsets are usually retained but may need a re-import in apps like Plex. M4A files don't show chapters in the iTunes Music library by design — for chapter-aware playback in Apple's stack, keep the original M4B.

Why convert M4B to M4A if the audio is the same?

The extension and the audiobook flag are what matter. Apple Books and iTunes route .m4b to the audiobooks library and remember playback position; everywhere else, that flag is a liability. Sonos may refuse the file, VLC may show one giant chapter, Android Auto may skip it, and DAWs may error on chapter atoms. Switching to .m4a removes the audiobook semantics and turns the file into plain audio that any AAC-aware player handles without quirks.

Can I convert a DRM-protected M4B from Audible or older iTunes?

No. M4B files purchased from Audible (legacy AA, current AAX) or downloaded from older iTunes audiobook purchases are wrapped in FairPlay or Audible's proprietary DRM. The file has to be decrypted first using the Audible account it was purchased on — XConvert and other browser-based tools cannot strip DRM. If your M4B was created locally (your own narration, a podcast archive, an AudioBookConverter build), the conversion runs without issue.

Should I re-encode or just copy the audio when converting?

Copy when the source is already AAC at a bitrate you're happy with — it's bit-perfect, faster, and avoids the small generation loss that every lossy re-encode introduces. Re-encode when you want to drop bitrate (audiobook downsizing), switch to mono (narration), change sample rate (48kHz → 44.1kHz), or swap codec (AAC → ALAC for archival). For long audiobooks, copying is almost always the right call.

What bitrate is best for a converted audiobook?

64kbps mono AAC is the sweet spot for spoken-word M4A. Voice contains far less spectral information than music, so 64kbps mono sounds nearly identical to 128kbps stereo for narration while being 4× smaller. Drop to 48kbps mono if you need every byte for a long book on a small device. Stay at 96kbps stereo if there's score, sound effects, or a full-cast dramatization.

Will the converted M4A play on my car stereo or Bluetooth speaker?

Almost always yes. AAC inside an M4A container is the most broadly supported lossy audio format outside of MP3 — it's required by the Bluetooth A2DP spec, supported by every modern car head unit, and decoded natively by Android, Windows, Linux, and Apple. The M4B-to-M4A conversion is what unlocks this compatibility for audiobooks that would otherwise be stuck inside Apple Books.

Can I split a long M4B into per-chapter M4A files?

Yes — use Audio Trim with start time and duration to pull a single chapter out as its own M4A. Repeat the upload with different trim values to extract each chapter. The file stays AAC inside an M4A container, so quality matches the source as long as you use Copy or a high enough bitrate.

Is there a file size limit?

XConvert processes files in your browser session, so the practical limit is your device's available memory. Most modern laptops handle multi-GB M4B audiobooks (40+ hours at 128kbps stereo is around 2.2GB) without issue. For very long files on a memory-constrained machine, trim into chapters first using Audio Trim.

What if I want a different output format instead?

Use Convert M4B to MP3 for universal Android and old-player compatibility, Convert M4B to WAV for uncompressed editing, or Convert M4B to FLAC for cross-platform lossless archival.