What is an M4B File?

How to Open, Edit, & Convert M4B Files

Picture of the M4B file icon used with iTunes

A file with the M4B file extension is an MPEG-4 Audio Book file. They're often seen used by iTunes to store audio books.

Some media players use the M4B format to store digital bookmarks along with the audio, letting you pause playback and then resume later. This is one reason they're preferred over MP3s, which can't save your place in the file.

The M4A audio format is basically identical to M4B except that those types of files are used for music instead of audio books.

Apple's iPhone uses the MPEG-4 Audio format for ringtones too, but those files are instead saved with the M4R extension.

How To Open an M4B File on an iPhone

iTunes is the primary program used to both play M4B files on a computer as well as to transfer audio books to an iPhone or other iOS device. You can do this by adding the audio books to iTunes and then syncing your device with iTunes.

Start by transferring the M4B file to iTunes. In Windows, use the File menu to choose either Add File to Library... or Add Folder to Library... to browse for the M4B file.

Note: If your audio books aren't in the M4B format, but instead are MP3s, WAVs, etc., skip down to the "How to Make an M4B File" section below to convert your audio files to the M4B format, and then return here to see what to do next.

With the device plugged in, click or tap the phone icon in iTunes to switch the window to the iOS device.

Choose the Audiobooks menu on the left side of iTunes. Put a checkmark next to Sync Audiobooks, and then pick whether you want to sync all the audio books from your iTunes library or just certain ones.

Now you can sync your device with iTunes to send the M4B file to your iPhone, iPad, or iPod touch.

How To Open an M4B File on a Computer

iTunes isn't the only program that will play an M4B file on a computer. Windows Media Player works too, but you may have to open Windows Media Player first and then open the M4B file manually since Windows may not recognize the M4B extension.

Another option is to rename the extension from .M4B to .M4A, because Windows does properly associate M4A files with Windows Media Player.

Other multi-format media players that natively support the very similar M4A format, like VLC and MPC-HC, will also play M4B files.

Tip: An M4B audio book that you purchase (versus one that you download for free from a site like LibriVox) is likely protected by DRM, meaning that it will only play using authorized computer software and devices. For example, most M4B based audio books that you purchase from the iTunes store are DRM protected and will play only in iTunes and devices authorized via iTunes.

How To Convert an M4B File

Since M4B files are often audio books, they're usually pretty large, and therefore are best converted with a dedicated, offline free file converter program. DVDVideoSoft's Free Studio is one free M4B file converter that can save the M4B to MP3, WAV, WMA, M4R, FLAC, and other audio formats.

Zamzar is another M4B converter but it runs in your browser, which means you have to upload the file to their website to have it converted. Zamzar can convert M4B to MP3 online, as well as to similar formats like AAC, M4A, and OGG.

Important: You cannot usually change a file extension (like the M4B file extension) to one that your computer recognizes and expect the newly renamed file to be usable. An actual file format conversion using one of the methods described above must take place in most cases. As I mentioned previously, however, try renaming the .M4B file to .M4A, a trick that is very often successful, at least for non-DRM protected M4B audio books.

How to Make an M4B File

If you want to put an audio book on your iPhone, but the audio file isn't in the M4B format, you'll have to convert the MP3, WAV, or whatever format the file is in, to M4B so that the iPhone won't mistake it for a song. Basically, you just have to do the opposite of what I described in the section above.

Audiobook Binder can convert MP3 to M4B on macOS. Windows users can download MP3 to iPod/iPhone Audio Book Converter to convert multiple MP3s to M4B files or even to combine the MP3s into one big audio book.

More Help With M4B Files

See Get More Help for information about contacting me on social networks or via email, posting on tech support forums, and more. Let me know what kinds of problems you're having with opening or using the M4B file and I'll see what I can do to help.