How audiobook chapters work
An M4B audiobook keeps its chapters as a list inside the file: a title and a start time for each one. Players such as Apple Books, BookPlayer and Audiobookshelf read that list to show chapter names and let you skip between them. Changing chapters only changes that list, so the editor rewrites it and copies the audio across untouched.
Where to put a chapter mark
A good chapter mark sits in the pause before the chapter’s first words, close enough that skipping to it doesn’t start on a long silence. The Chapter River finds the pauses as it draws the waveform and snaps each buoy to the end of the nearest pause, half a second before the voice returns.
Shortcuts on the river
| Do this | To |
|---|---|
| Drag a buoy | Move a chapter (it snaps to pauses) |
| Double-click the waveform | Add a chapter there |
| Double-click a buoy | Hear five seconds around the cut |
| Click the waveform | Move the playhead |
| Wheel, or + and − | Zoom in and out |
| Drag the waveform or the strip below it | Scroll through the book |
| ← →, with Shift for bigger steps | Nudge the selected chapter |
| ↑ ↓, Enter, Delete | Pick a chapter, listen to it, remove it |
| Ctrl+Z, Ctrl+Shift+Z | Undo and redo |
Which files work
- M4B and M4A: chapters are written as standard MP4 chapters (Nero and QuickTime styles) for the widest player support.
- MP3: chapters are written as ID3v2 chapter frames, read by many podcast and audiobook apps.
- Other formats, such as FLAC or WAV, can be turned into an M4B first with the MP3 to M4B maker.