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chapterpass

Automatic audiobook
mastering in minutes

chapterpass formats your voice recordings to meet Audible’s strict ACX technical standards. Drop a file in, get a submission-ready file out.

Accepted formats: WAV, MP3, FLAC, AIFF, M4A. Maximum duration 120 minutes.

Drop your chapter files here

or browse files

WAVMP3FLACAIFFM4A
Your audio never leaves your deviceFirst file freeNo account neededWorks in your browser

Example output

Every file comes back with a report

Sample compliance report Every spec met

Chapter 01_cp.mp3

Your audio versus ACX/Audible spec

RMSPassMeasured-20.30Target-23 to -18
True peak (dBFS)PassMeasured-3.80Targetbelow -3
Noise floor (dBFS)PassMeasured-64.50Targetbelow -60
Sample rate (Hz)PassMeasured44100Target44100
ChannelsPassMeasuredMonoTargetMono or stereo
Head silence (s)PassMeasured1.50Target1 to 5
Tail silence (s)PassMeasured1.50Target1 to 5
Output formatPassMeasured192 kbps CBRTarget192 kbps CBR

8/8 checks passed

ACX/Audible spec

This is the same report you get for every file: each spec measured, with the ACX target beside it. Targets sourced from ACX: Audio Submission Requirements. For what each number means, read the ACX audio specs guide.

How it works

Three steps, all in your browser

  1. Drop in your chapters

    Drop your edited recordings straight into this browser tab. No account, no install, nothing to configure.

  2. Mastered on your device

    chapterpass levels loudness, controls peaks, manages the noise floor, sets the right format, pads the silences, and masters every file to the ACX spec.

  3. Download your masters

    Save ACX-ready files in minutes, each with its own compliance report. Your first chapter is free, so you can hear it before you pay.

Private by design

  • Runs in your browser

    All mastering happens locally in WebAssembly, on your own machine.

  • Never uploaded

    Your recordings stay in this tab. Your audio never leaves your browser.

  • Nothing stored

    We keep no copy of your audio. Close the tab and nothing of yours remains.

Who does what

Audiobook submission, sorted

We handle

6 checks
  • Loudness
  • Peak control
  • Noise floor
  • Head & tail silence padding
  • Compliant MP3 export
  • Compliance report

You bring

4 inputs
  • Clean recording
  • Consistent narration
  • Opening & closing credits
  • One chapter per file

Pricing

Know the cost before you start

Under 5 hrs

$36/ finished hr

5-10 hrs

$27/ finished hr

10+ hrs

Best rate

$18/ finished hr

A 10-hour audiobook, three ways to get ACX-ready

Human engineer$700-1,2003-7 days

IP exposure, communication overhead

AudacityFree2-10+ hrs

Steep learning curve

chapterpass$180a few min

Private, deterministic, report-backed

Free

Your first file

Built for narrators

“This. Is. Brilliant. This takes QC and mastering from where I started at 5 hours per 1 hour of audio to maybe 2 total for a 10 hour book. It’s mind blowing. Thanks for creating chapterpass!!!”

Laura G.

Multiple Earphones Award Winner, Audie Award Finalist, SOVAS Voice Arts Winner

Guides

Guides to get you ACX-ready

Browse the full library of ACX audiobook mastering guides, read the mastering tool comparison, or see where your file stands with the free ACX check.

FAQ

Questions, answered

Do my files leave my computer?
No. All processing runs locally in your browser via WebAssembly. Your audio files are never uploaded to a server, never stored remotely, and never accessible to anyone but you.
How much does chapterpass cost?
Your first file is free, no account or payment needed. After that, pricing depends on total audio length: under 5 hours costs $36 per finished hour, 5 to 10 hours costs $27 per finished hour, and 10+ hours costs $18 per finished hour. You see the exact price before you pay. No subscriptions, no hidden fees. Each order takes up to 15 hours and 100 files; split a longer book into two orders.
Does chapterpass guarantee my audiobook will pass platform quality review?
No. chapterpass handles the measurable technical specs: loudness, peaks, noise floor, format, and silence. ACX also runs a human quality review that listens for clicks, pops, mouth noise, echo, pacing, and manuscript accuracy. Recording quality issues will still cause rejection regardless of what chapterpass does to the technical numbers.
Does chapterpass remove clicks, pops, or mouth noise?
No. chapterpass adjusts loudness, limits peaks, manages noise floor in silent sections, and converts to the right format. It does not edit the content of your narration. Removing clicks, pops, mouth noise, or other recording artefacts needs to happen in your recording software before you upload.
Do I need a DAW to use chapterpass?
Not for the technical mastering. That is what chapterpass replaces. You will still need a way to record and edit your narration (remove mistakes, clean up audio, add credits). That could be a DAW or a simpler audio editor like Audacity. Once your edited recording is ready, chapterpass handles the mastering step.
Should I use Audacity, hire a mastering engineer, or use chapterpass?
All three routes produce distribution-ready files. Audacity is free and gives you full control, but you configure four effects, run a macro, and verify results manually. Hiring a mastering engineer is hands-off: you send files, you receive mastered files, typically hundreds of dollars per finished hour. chapterpass sits between: drop a file in, get a verified file out, $18 to $36 per finished hour, first file free, files stay on your device.

More questions? The full FAQ page has the complete list of answers.

Start free

Master your first file free

Drop a chapter in, see the report, download a submission-ready file. No account, no card.

Get startedRun the free ACX check