ACX Audio Submission Requirements

Create top-quality audiobooks, and maximize your sales potential by providing the best overall listening experience.

Audiobooks uploaded to ACX must adhere to the following requirements. The ACX Quality Assurance team may reject titles that do not meet these standards, and their retail release may be delayed. The following requirements help ensure customers get a great listen.

Your submitted audiobook must:

Each uploaded audio file must:

More information on how to meet these requirements can be found below and in our Video Lessons & Resources, and many of the terms used here can be found in our Audio Terminology Glossary.

Your submitted audiobook must be consistent in overall sound and formatting.

Consistency in audio levels, tone, noise level, spacing, and pronunciation gives the listener an enjoyable experience. Drastic changes can be jarring to the listener and are not reflective of a professional production. This distracts from the listening experience and may lead to poor reviews and reduced sales.

Each uploaded file must be free of extraneous sounds such as plosives, mic pops, mouse clicks, excessive mouth noise, and outtakes.

Extraneous sounds can distract listeners from the story, and outtakes sound unprofessional. Each can elicit bad reviews and bad reviews can hurt sales.

Your audiobook must include opening and closing credits that match the title’s cover art.

At minimum, the opening credits must note the name of the audiobook, the name of the author(s), and the name of the narrator(s). Closing credits must, at minimum, state “the end”.

Opening Credits Minimum Requirements
“[title of audiobook]”
“(subtitle if applicable)”
Written by [name of author]
Narrated by [name of narrator]
Closing Credits Minimum Requirements
The End


Your audiobook must include a retail audio sample that is between one and five minutes long. Explicit material is not permitted in the sample.

This sample should start with narration, not opening credits or music. The sample must not include explicit material. This sample is used by customers to preview of your audiobook.

Each file must contain only one chapter or section.

You’ll be prompted to upload each file individually. Both the opening credits and closing credits must be separate files. This ensures listeners can easily navigate between sections, and that skipping forwards or backwards moves them forward or back one section.

Each file must have 0.5 to 1 second of room tone at its beginning and 1 to 5 seconds of room tone at its end.

This space is required to ensure titles are successfully encoded in the many formats made available to customers. It also gives listeners an audio cue that they have reached the beginning or end of a section.

Each file must contain the section header, if contained within the manuscript (e.g., “Prologue”, “Chapter 1”, “Chapter 2”).

These announcements help the listener understand what section of the book they are listening to without having to look at their player. If a section header is found to be missing during the ACX QA review, you will be contacted to make revisions which could delay the release of your title. Be consistent – a listener may think content is missing if most headers are read but some are not .

Each file must measure between -23dB and -18dB RMS.

Put simply, all files must fall within a specific volume range. By keeping all files within this range – not too loud and not too soft – listeners won’t have to constantly adjust the volume of their playback device.

Each file must have peak values no higher than -3dB.

By leaving this headroom you’ll reduce the possibility of distortion, which can reduce the quality of the listening experience. This headroom is also needed to ensure files are successfully encoded.

Each file must have a noise floor no higher than -60dB RMS.

Noisy files that contain background sounds and other distractions make it difficult for listeners to focus on the material.

Each file must be 192kbps or higher 44.1kHz MP3, Constant Bit Rate (CBR).

Before going on sale in the Audible store, titles are encoded in a variety of formats that customers have the option of downloading. 192kbps (or higher), Constant Bit Rate MP3 files are required so this encoding process works without error. You may upload 256kbps or 320kbps files if you’d like, but the difference in quality heard by listeners will be negligible. Please see our tutorial for creating MP3s to our spec if this work is unfamiliar to you.

All files must be the same channel format (All mono or all stereo files).

Submitted audiobooks may not contain both mono and stereo files. Stereo files must not be joint-stereo. Mono files are strongly recommended. Before being added to the Audible store, submitted audiobooks are encoded in a variety of formats that listeners have the option of downloading. Titles submitted with both stereo and mono files will cause errors during this encoding process and the title’s retail release may be delayed. We recommend mono for all of your files as this may prove to be the smoothest path that also allows for audio consistency.

Each file must be no longer than 120 minutes.

Files over 120 minutes are not supported. If a section will be over 120 minutes long, find a good break in the narration and split the section into two files. A secondary section header must be included on continuations. If the section began with a header, such as “Chapter 2”, we recommend starting the second file with “Chapter 2 continued”. This will help ensure listeners can easily navigate from section to section.

Your submitted audiobook must be narrated by a human.

Text-to-speech recordings are not allowed. Audible listeners choose audiobooks for the performance of the material, as well as the story. To meet that expectation, your audiobook must be recorded by a human.