Complete ACX Submission Guide for 2026: From Manuscript to Audible

ACX is the gateway to Audible, Amazon, and Apple Books — the three largest audiobook platforms in the world. Getting your audiobook accepted requires meeting specific technical and content standards. This guide walks you through every requirement so your submission passes on the first try.

Audio Technical Requirements

ACX is particular about audio specifications. Every file must meet these standards:

• Format: MP3 at 192 kbps or higher, constant bit rate (CBR)
• Sample rate: 44.1 kHz
• Channels: Mono (single channel)
• Peak volume: Must not exceed -3 dB
• RMS level: Between -23 dB and -18 dB
• Noise floor: Below -60 dB
• Room tone: 0.5 to 1 second of silence at the beginning and end of each file

AI audiobook tools that are designed for ACX compliance handle these specifications automatically. If you are producing manually, check every file with ACX's free Audio Lab tool before submitting.

File Structure

Your audiobook must be submitted as individual chapter files, not a single long recording. Each file should be named consistently — ACX recommends a sequential naming convention like 001_opening_credits.mp3, 002_chapter_one.mp3, etc.

You need an opening credits file (title, author, narrator) and a closing credits file at minimum. Each chapter file should be between 30 seconds and 120 minutes in length. Most chapters fall between 15 and 45 minutes.

Content Requirements

Your audiobook must be at least 3 hours long to qualify for Audible distribution. The narration must match the submitted text exactly — no improvisation, no skipping sections, no paraphrasing. ACX QC reviewers compare the audio against the text.

The opening credits must include the book title, author name, and narrator credit. The closing credits should include the same information plus an indication that the book has ended, such as "This has been [Title] by [Author], narrated by [Narrator]."

Common Rejection Reasons

• Audio levels outside spec — most common. Check RMS and peak levels carefully.
• Background noise — hum, hiss, room echo, or inconsistent noise floor.
• Plosives and sibilance — harsh "p" and "s" sounds that were not de-essed.
• Missing room tone — every file needs silence padding at start and end.
• Inconsistent volume — chapter-to-chapter variation in loudness.
• Retail audio sample issues — your 1-to-5-minute sample must also meet all specs.

Rights and Distribution

ACX offers two distribution arrangements. Exclusive distribution gives Audible, Amazon, and Apple Books exclusive rights for 7 years in exchange for a 40% royalty rate. Non-exclusive distribution lets you sell on other platforms but drops your royalty to 25%.

For most independent authors, non-exclusive is the better choice. It gives you freedom to sell on Findaway, Google Play, Spotify, and your own website while still reaching Audible's massive audience.

The AI Narration Question

ACX updated its policy on AI narration in 2024. AI-narrated audiobooks are now accepted on ACX as long as they are properly disclosed. You must indicate that the audiobook uses AI narration in your submission metadata. The quality bar remains the same — AI or human, the audio must meet all technical specifications.

Related Reading