Audible is the store; ACX is the marketplace many independent rights holders use to reach it. Understanding the difference avoids confusion.
Audible
Audible is Amazon's audiobook store and membership service. Listeners buy titles or use membership credits.
ACX
ACX connects rights holders with narrators and producers and distributes finished audiobooks to Audible, Amazon and Apple Books. Rights holders choose between exclusive and non-exclusive distribution, which carry different royalty rates.
Narration requirements
ACX standard submissions require human narration. Amazon offers synthetic narration only through its own authorized programs, such as the invite-only KDP Virtual Voice beta, and ACX has documented a narrator Voice Replica beta.
Audio review
Every ACX title passes an audio review against published technical requirements before going on sale.
Official sources
This article is general information, not legal or financial advice. Platform policies change — please check official sources.