What Is the Audible Format?

About this proprietary digital audio standard

Audible is a popular audiobook and spoken-word platform. When you purchase a book, podcast, or another spoken-word title from Audible, it's added to your account and delivered to you as an audio file.

Here's a look at the proprietary Audible format and how to listen to your spoken-word downloads.

When you buy a book from Audible, it's yours forever. If Audible retires a format, you'll be able to download the title again in a new, improved format.

Audible logo

Downloading an Audible Title

When you purchase a title on Audible and add it to your library, you have the option to Listen Now or Download. If you're on a computer and select Listen Now, your title begins playing immediately via the Audible Cloud Player, which streams your title on a Windows PC or Mac. If you select Download, the file downloads to your computer in Audible's proprietary .aax format.

If you use the Audible app for iOS, Android, Windows Phone, an Alexa-enabled device, Fire TV, or another supported device, you can stream the title from your device or download it and add it to your library, so you can listen to it whenever you want, even when you're not on Wi-Fi.

About Audible's Proprietary File Format

When you purchase a book on Audible, you used to have the option of downloading the file in Enhanced format (.aax) or Format 4 (.aa).

Audible File Format Downloads

However, as of June 2020, Audible has phased out Format 4 (.aa) and will only support Enhanced format (.aax). If you previously purchased a title in Format 4, you can download it again in the currently supported format.

The Audible formats .aa and .aax covered a range of encoded bitrates. These sound formats were designed to give you a choice about the sound quality level you wanted when you downloaded your audiobooks. With Format 4 (.aa), the sound was encoded at 32 Kbps, and the quality of sound was categorized at standard MP3 level. With Enhanced (.aax), the sound is encoded at 64 Kbps and is deemed as having CD-quality sound.

As devices have improved, Audible decided to stop supporting Format 4, aiming to provide users with a higher-quality listening experience. Having the Format 4 choice made sense when more people had older devices that didn't support Audible's Enhanced bitrates, but this is no longer the case.

Earlier versions of Audible's proprietary format included Format 2, which had a bitrate of 8 Kbps and sound on par with AM radio, and Format 3, with a bitrate of 16 Kbps and sound on par with FM radio. Both of these formats had the .aa file extension.

About Audible File Format Conversions

You can't convert Audible audio files from the .aax format to another format, such as MP3. Audible's proprietary .aax format has security technologies that protect the intellectual property rights of content providers, while offering an enhanced listening experience for users.

  • Why can't I play an AA/AAX file from Audible on Paperwhite?

    Although older Kindle models support audiobook files with MP3, AA, and AAX extensions, the Kindle Paperwhite doesn't support these DRM-protected formats. The Paperwhite supports MOBI to AZW, AZW extension, unprotected PRC, and PDF to TXT.

  • How do I convert an Audible AA file to an MP3?

    The best way to convert an Audible AA file is with an audible converter such as TuneFab, which converts the AA/AAX format to MP3, as well as M4A, FLAC, or WAV file formats.

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