Choosing where to distribute your audiobook determines your retail reach, royalty rate, exclusivity obligations, and technical specifications. The major platforms (ACX/Audible, Findaway Voices (Voices by INaudio), Author's Republic, Google Play Books, and Kobo) each have different business terms and audio requirements. This comparison covers all five side by side so you can make an informed decision.[1]
If you're looking specifically at audio specification differences between platforms, the ACX vs Findaway requirements comparison covers the technical side in greater detail.
What Makes ACX/Audible the Dominant Platform?
ACX is Amazon's audiobook creation and distribution platform. Publishing through ACX places your audiobook on Audible, Amazon, and Apple Books. Audible holds an estimated 60–65% of US audiobook sales, though published estimates range from 63% to over 90% depending on methodology, and no single authoritative public figure exists.[2] That dominance makes ACX the most important single channel for most audiobook producers.
ACX Technical Requirements
ACX enforces the strictest automated quality checks in the industry. Every chapter file must pass all eight specifications:[1]
- RMS Loudness: -23 to -18 dBFS
- True Peak: below -3 dBFS
- Noise Floor: below -60 dBFS
- Sample Rate: 44,100 Hz
- Channels: Mono only
- Format: MP3, 192 kbps CBR
- Head Silence: 0.5 to 1 second
- Tail Silence: 1 to 5 seconds
Files that fail any single spec get rejected automatically with no manual override. The complete ACX audio requirements guide explains each specification in depth.
How Does the ACX Royalty Structure Work?
ACX offers two distribution options with different royalty splits:
Exclusive distribution locks your audiobook to Audible, Amazon, and Apple Books for seven years. The standard royalty share is 40% of net sales. If you used ACX's royalty-share model (splitting royalties with a narrator instead of paying upfront), both parties receive 20%.
Non-exclusive distribution gives you a 25% royalty share but allows simultaneous distribution through other platforms. The non-exclusive term is also seven years.[3]
New royalty model (November 2024, early access): ACX announced a revised model where exclusive authors earn 50% and non-exclusive authors earn 30%, calculated on "Member Value" rather than list price. As of early 2026 this model is in early access and available by opt-in.[4]
ACX Strengths and Limitations
ACX's primary strength is access to Audible, the single largest audiobook retailer. The platform also offers a production marketplace where rights holders can connect with narrators.
The limitations are significant: the seven-year commitment is long, the standard royalty rates are lower than what you'd earn selling direct, and the exclusive option means giving up all other channels. ACX does not distribute to libraries, Scribd, or most international retailers beyond Apple Books.
How Does Findaway Voices Compare to ACX?
Findaway Voices, rebranded as Voices by INaudio in August 2025, is the largest wide-distribution aggregator for audiobooks. Where ACX gives you access to three retailers, Findaway distributes to over 40 retailers and library platforms worldwide including Apple Books, Kobo, Google Play, Scribd, Chirp, Storytel, OverDrive, and Hoopla.[5]
Findaway Technical Requirements
Findaway's audio specifications closely mirror ACX:
- RMS Loudness: -23 to -18 dBFS
- True Peak: below -3 dBFS
- Noise Floor: below -60 dBFS
- Sample Rate: 44,100 Hz
- Channels: Mono or stereo (joint stereo recommended for stereo files)
- Format: MP3 192 kbps CBR or FLAC
- Head Silence: 0.5 to 1 second
- Tail Silence: 1 to 5 seconds
The key differences: Findaway accepts stereo files and FLAC format. In practice, if your files pass ACX's automated checks, they will pass Findaway's requirements. Master once to ACX specs and distribute everywhere.
Findaway Royalty Structure
Findaway keeps 20% of net sales and passes 80% to you, a flat rate with no exclusivity requirement. Different retailers within Findaway's network pay different wholesale prices, so your effective per-sale revenue varies by channel. There is no upfront cost to distribute through Findaway beyond producing your audiobook.
Findaway Strengths and Limitations
Findaway's reach is unmatched for wide distribution. If you want your audiobook in libraries, on Scribd, on Kobo, on Google Play, and on dozens of smaller retailers, Findaway is the most efficient path. The non-exclusive model means you can use Findaway alongside ACX non-exclusive without conflict.
The limitation is that Findaway is a middleman. You have less control over pricing and merchandising compared to direct uploads. Findaway also doesn't distribute to Audible. That channel requires ACX.
What Does Author's Republic Offer?
Author's Republic is another wide-distribution aggregator, now part of the Findaway/Spotify ecosystem. They distribute to over 30 retailers and library platforms with a focus on indie authors and small publishers.[6]
Author's Republic Technical Requirements
Author's Republic specifies requirements that match ACX:
- RMS Loudness: -23 to -18 dBFS
- True Peak: below -3 dBFS
- Noise Floor: below -60 dBFS
- Sample Rate: 44,100 Hz
- Channels: Mono or stereo (all files must match)
- Format: MP3, 192 kbps CBR
- File Size: under 170 MB per file
- Duration: under 119 minutes per file
- Silence: 1 to 5 seconds at head and tail
The file size and duration limits are more restrictive than ACX for very long chapters. If your chapters are under two hours each, this won't affect you.
Author's Republic Royalty Structure
Author's Republic uses a tiered royalty model. The self-produced tier keeps 30% and passes 70% to you. Like Findaway, there are no exclusivity requirements.[6]
Author's Republic Strengths and Limitations
Author's Republic offers wide distribution with a straightforward dashboard. Their overlap with Findaway's retail network is significant, so using both simultaneously provides diminishing returns. The 70/30 split (self-produced tier) is less favourable than Findaway's 80/20, which is worth considering if you're choosing between the two for wide distribution.
What Are Google Play Books' Requirements?
Google Play Books accepts direct audiobook uploads through the Google Play Books Partner Centre. This means you can skip aggregators entirely and upload directly to Google's platform.[7]
Google Play Technical Requirements
Google has the most flexible format requirements of any major retailer:
- Formats: MP3, AAC/M4A, FLAC, or WAV
- MP3 Bitrate: 128 kbps minimum (mono) or 256 kbps (stereo), CBR preferred
- Lossless: 16-bit, 44.1 kHz or higher
- Silence: recommended but no strict duration specified
Google does not publish specific RMS, peak, or noise floor targets. They apply their own processing on ingestion. Files mastered to ACX specs will work fine because ACX's targets already represent industry best practice for spoken word.
Google Play Royalty Structure
Google offers a 52/48 revenue split: you keep 52%, Google keeps 48%. This applies to purchases. For Google Play's subscription listening programme, payouts are based on listening time and vary.
Google Play Strengths and Limitations
Direct upload means no aggregator fee. Google Play has growing audiobook market share, particularly on Android devices where Google Play Books comes pre-installed. The 52% royalty rate is reasonable for a direct retailer relationship but not as favourable as selling from your own website.
How Does Kobo Writing Life Handle Audiobooks?
Kobo accepts audiobook uploads through their Writing Life self-publishing platform. Kobo distributes to their own retail platform and the Walmart audiobook store.[8]
Kobo Technical Requirements
Kobo's published requirements focus on format rather than loudness:
- Format: MP3
- File Size: under 200 MB per file, 2 GB total
- Compression: Kobo compresses to 64 kbps on ingestion
Kobo does not publish specific RMS, peak, or noise floor targets. Their compression on ingestion means your source file quality matters less than on platforms that deliver your file as-is. Files mastered to ACX specs will work without modification.
Kobo Royalty Structure
Kobo offers a 55/45 revenue split for audiobooks: you keep 55%. There are no exclusivity requirements.
Kobo Strengths and Limitations
Kobo has strong market presence in Canada, the UK, and parts of Europe. The Walmart partnership provides access to a large retail channel that other platforms don't reach. However, Kobo's overall audiobook market share is modest compared to Audible.
Which Distribution Strategy Should You Choose?
The answer for most independent audiobook producers is not one platform; it's a combination.
The Standard Strategy
The most common approach is ACX non-exclusive plus a wide distributor. For a complete walkthrough of the self-publishing process from recording to distribution, see the self-publishing audiobook guide.
- ACX non-exclusive for the Audible/Amazon/Apple Books channel (25% royalty, or 30% under the new model if available)
- Findaway Voices for everything else: libraries, Scribd, Kobo, Google Play, and international retailers (80% of net)
This gives you maximum reach without exclusivity lock-in. You sacrifice royalty percentage on the ACX channel compared to exclusive, but you gain access to every other retail and library channel.
When Does ACX Exclusive Make Sense?
Choose ACX exclusive only if you're confident that Audible will generate the vast majority of your sales and the royalty premium (40% vs 25% standard, or 50% vs 30% under the new model) justifies losing all other channels for seven years. For established authors with strong Audible readership, this can be the right call. For debut titles or authors building a catalogue, the lock-in usually isn't worth it.
What About Direct Uploads?
If you want maximum control and are willing to manage multiple dashboards, you can skip aggregators for platforms that accept direct uploads:
- ACX for Audible/Amazon/Apple Books
- Google Play Books direct upload
- Kobo Writing Life direct upload
- Findaway Voices for retailers that don't accept direct uploads (libraries, Scribd, Storytel, international stores)
This approach is more work but avoids paying aggregator fees for channels where direct access is available.
Do You Need Different Audio Masters for Each Platform?
No. ACX has the strictest automated requirements of any distributor. Files that pass ACX's eight-point quality check will meet or exceed the requirements of every other major platform.[1]
This means your mastering workflow is the same whether you're distributing to one platform or ten. Master to ACX specs (RMS between -23 and -18 dBFS, true peak below -3 dBFS, noise floor below -60 dBFS, mono MP3 192 kbps CBR at 44.1 kHz) and your files work everywhere. For a detailed breakdown of each platform's format specifications, see the audiobook format requirements guide.
For a step-by-step guide to meeting these specifications, see the complete audiobook mastering guide. For a quick reference of ACX's specific requirements, see the platform page.
Master once, distribute everywhere. ChapterPass masters your audiobook to ACX specifications, the strictest standard in the industry. Your files will pass quality checks on every major distribution platform.