Split Audiobook by Silence: auto chapter breaks

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 a long file

One MP3, M4B, WAV or FLAC with no chapters, such as a recording or a single-file audiobook.

Let it listen

The whole file is measured on your device, and every pause appears on the waveform.

Tune the breaks

Set how long a pause must be and how short a chapter may get, then drag, add or remove breaks.

Split or chapter

Download one file per chapter as a ZIP, or keep one file with the chapters added.

Pauses, chapters and the noise floor

Every recording has a quietest level: the hiss of the room and the microphone, called the noise floor. Narration sits well above it, and pauses drop back down to it. The splitter sets its silence line 12 dB above that floor, so it adapts to studio recordings and home recordings alike. You can move the line yourself if the automatic one misses quiet pauses or catches soft speech.

Choosing good breaks

Pause at least filters out the short gaps between sentences. Chapter breaks are usually 2 seconds or longer.
Chapters at least stops two breaks landing close together. The longest pauses win.
Every break sits just before the voice returns, so a chapter never starts with a long silence.

Already have an M4B with chapters you want to change? The chapter editor edits them directly, and the M4B chapter splitter cuts at existing chapters.

Questions, answered.

How does splitting by silence work?

The tool measures the loudness of every tenth of a second of the file and marks the stretches that are close to the room’s noise floor as pauses. The longest pauses become chapter breaks, as long as each chapter stays longer than the minimum you set.

What settings should I use for an audiobook?

Chapter breaks in narration are usually longer than the pauses between sentences: start with pauses of at least 2 seconds and chapters of at least 5 to 10 minutes. If too many breaks appear, raise either value; if a break is missing, lower the pause length or add it by double-clicking the waveform.

Can I keep one file and just add chapters?

Yes. For M4B, M4A and MP3 files, choose “One file, chaptered”. The breaks are written as chapters and the audio is copied without re-encoding.

Is splitting lossless?

For M4B and M4A files, “Original quality” copies the audio exactly. MP3 and other formats are split into MP3 files at the quality you choose, cut exactly at the breaks with no clicks.

Why does it take a while before breaks appear?

Finding pauses means decoding the whole file. That happens on your computer, at many times real-time speed, and breaks appear as the file is measured. The first time, the audio engine (about 31 MB) downloads once.

Is my file uploaded?

No. Everything happens in your browser and the file never leaves your device.