What is an M4B file?
M4B stands for MPEG-4 audiobook. It was created by Apple and first released in 2003. M4B is an M4A file that remembers your place and carries chapter markers, which is why audiobook apps prefer it. Converting it to a single MP3 keeps the audio but loses the chapters.
| Type | audio |
|---|---|
| Compression | Lossy |
| Usually contains | AAC audio with chapter markers |
| In a browser | plays in browsers that play M4A, and in Apple Books |
| Common uses | audiobooks from iTunes and Audible-style downloads |
| MIME type | audio/mp4 |
Which format should you convert M4B to?
- M4B to MP3 to play on any device, car stereo or website.
- M4B to M4A for iPhone, iTunes and Apple Music.
- M4B to MP4 to upload somewhere that only accepts video.
M4B is already lossy, so converting it to a lossless format makes the file bigger without improving it; pick a lossless target only if a program requires one.
How to open an M4B file
Whether an M4B file opens with a double click depends on the device. Here is what works on each, without buying software:
| Windows | Films and TV and Media Player open the common formats; VLC opens almost any audio file, M4B included. |
|---|---|
| Mac | QuickTime Player opens formats Apple supports; VLC or IINA open the rest. |
| iPhone and iPad | The Files app plays formats Apple supports. For others, a player such as VLC for iOS, or converting the file here, is the easiest route. |
| Android | Most gallery and music apps play the common formats; VLC for Android plays almost everything. |
| Web browser | M4B plays in browsers that play M4A, and in Apple Books. |
Want the technical details? See what a .m4b file is, with its MIME type, file signature and a viewer.
M4B compared with other audio formats
How M4B stacks up against the formats people most often convert it to or from:
| Format | Compression | Usually contains | Released | Best for |
|---|---|---|---|---|
| M4B | Lossy | AAC audio with chapter markers | 2003 | audiobooks from iTunes and Audible-style downloads |
| MP3 | Lossy | MP3 audio, typically 128 to 320 kbps | 1993 | music libraries, podcasts and anything that has to play everywhere |
| WAV | Lossless | uncompressed PCM, usually 16-bit at 44.1 or 48 kHz | 1991 | recording, editing, sound effects and CD audio |
| M4A | Either | AAC, or ALAC for lossless files | 2001 | iTunes purchases, iPhone voice memos and Apple Music downloads |
| FLAC | Lossless | FLAC lossless audio, up to 32-bit and 655 kHz | 2001 | CD rips, hi-res music stores and audio archives |
How to use the M4B converter
- Choose the format you want in the Convert to menu.
- Drop your M4B files on the box, or press Choose M4B files. Several files can go in at once.
- Adjust the settings if you need to; the defaults suit most people.
- Press Convert and save each file with its Download button. Nothing is uploaded at any point.
Tips for converting M4B files without losing quality
M4B is lossy, so some detail was already discarded when the file was made. Converting it cannot bring that back. Converting to a lossless format preserves what is left exactly but makes the file larger; converting to another lossy format adds a small extra loss, which is invisible at sensible settings.
- Keep a lossless master. If you have WAV, FLAC, AIFF or ALAC, keep it, and make lossy copies such as MP3 or AAC from it when you need them.
- Avoid converting one lossy format into another more than once. Each MP3, AAC or OGG encode throws away a little more, and the losses add up.
- Match the bitrate to the content: 192 kbps and up for music, 96 to 128 kbps for podcasts, 64 kbps for voice notes.
- Stick to 44.1 kHz for music and 48 kHz for audio that goes with video; resampling between them is harmless but pointless.
Convert M4B files from the command line
Everything this page does can also be done in a terminal. The most common M4B conversion, to MP3, looks like this with ffmpeg:
ffmpeg -i input.m4b -vn -c:a libmp3lame -b:a 192k output.mp3Change the output extension to pick another format. The converter above runs the same ffmpeg engine inside your browser, so you get the result without installing anything.
M4B converter FAQ
What is an M4B file?
M4B stands for MPEG-4 audiobook, an audio format created by Apple in 2003. M4B is an M4A file that remembers your place and carries chapter markers, which is why audiobook apps prefer it. Converting it to a single MP3 keeps the audio but loses the chapters.
How do I open an M4B file?
M4B plays in browsers that play M4A, and in Apple Books. If the program you need will not open it, convert it to a more widely supported format above.
What is the most common M4B conversion?
M4B to MP3 is the conversion people search for most. The audio is decoded and written as MP3 at 192 kbps.
Does converting M4B files here upload them?
No. Every conversion on this page runs inside your browser, so your M4B files never leave your device.
Is the M4B converter free?
Yes. There is no sign-up and no watermark, and no limit on how many M4B files you convert. The site is supported by advertising.
Can I convert M4B files on iPhone or Android?
Yes. Open this page in Safari on iPhone and iPad, or in Chrome on Android, choose your M4B files and download the results to your Downloads folder.
Can I convert several M4B files at once?
Yes. Drop as many as you like; they are converted one after another, each with its own download button.