M4B Splitter: split by chapter or cut a section, free

Where it runs

Works in a current Chrome, Edge, Firefox or Safari, on Windows, Mac, Linux and Chromebook computers, Android phones, iPhones and iPads. Nothing to install, no account.

The first file loads the audio engine (ffmpeg, about 31 MB) once, and your browser keeps it. Very long books are easiest on a computer, which has more memory than a phone.

4 simple steps.

Drop your M4B

Every chapter marker in the file appears on the ribbon and in the list.

Pick chapters

Click chapters on the ribbon or tick them in the list. All are selected to start.

Choose a format

Keep the original quality with no re-encoding, or convert each chapter to MP3.

Download the set

Get every chapter as its own tagged, numbered file in one ZIP.

Splitting at chapter markers

An M4B audiobook stores a list of chapters: a title and a start time for each. The splitter reads that list straight from the file and cuts the book exactly at those points, so each output file is one complete chapter, named after it.

Cutting out a section

As an audiobook cutter, the splitter trims one stretch out of a book: a scene to share, a passage for a narrator to re-record, a sample, or just the part you want to keep. Choose A section, type the start and end, and listen to the edges before you cut. In original quality the cut lands on the nearest AAC frame, about a fiftieth of a second; as MP3 it is exact. For a retail sample with ACX’s length and loudness rules, the sample maker does it for you.

Original quality or MP3?

	Original quality (M4A)	MP3
Speed	Very fast, no re-encoding	Slower, every chapter re-encoded
Quality	Identical to the source	Slight loss, depends on bitrate
Cut accuracy	About 0.02 s	Exact to the sample
Plays on	Phones, computers, most apps	Almost every device

Good uses for chapter files

Players and car stereos that handle short files better than one long book.
Sharing or reviewing a single chapter with a narrator or editor.
Rebuilding a book with a different order or chapter names in the MP3 to M4B maker.

Questions, answered.

How do I split an M4B into chapters?

Drop the M4B here. Its chapters are read instantly; choose which ones you want, pick “Original quality” or MP3, and press the button. Each chapter becomes its own file, and you can download them all as a ZIP.

Does splitting lose quality?

Not with “Original quality”. The audio is copied exactly as it is, with no re-encoding, into M4A files, which is also the fastest option. Chapter cuts are accurate to about two hundredths of a second.

Can I cut out just one section?

Yes. Choose “A section”, then type a start and an end (like 1:02:30), or fill them from a chapter. Listen to the first and last five seconds before you cut. The section is saved as its own file: M4A with no re-encoding, or MP3. It works on MP3 audiobooks too.

What if the M4B has no chapters?

The splitter switches to equal parts: choose a length between 5 and 120 minutes and the book is cut into evenly sized files.

Are the split files tagged?

Yes. Every file gets the chapter title, the book as the album, the author, narrator, genre, a track number and the cover art.

Is there a size limit?

There is no upload, so there is no upload limit. Very large books are limited only by your browser’s memory; a typical computer handles books of 20 hours or more.

Can I join the chapters back together?

Yes. Use the MP3 to M4B maker: drop the files in, and each one becomes a chapter again.