What to Do When Audible Books are Stored as MP4 Files?

Posted by Adam Gorden on Dec 1, 2021 2:20 PM.

"I don't like using anything other than MP3 to listen to my audio, so in the past I'd download an Audiblebook and then convert those Audible AAX audiobooks to MP3. But now ot doesn't appear that option exists. All downloadable Audible books are saved as MP4 files now. What happened? Is there a way to save Audible AAX files from MP4 to AAX?"

Recently, there are a few comments that the titles downloaded from the Audible website are saved in MP4 format instead of AAX. This often happens to those users who use the Firefox to download Audible audiobooks. But til now, both Firefox and Audible don't make any response to this problem. To help get your Audible audiobooks playing properly, we've provided a step-by-step instruction on how to resolve it. Let us take a look at how to change Audible from MP4 to AAX, as well as, how to convert Audible books to MP3.

audible mp4

Part 1. Why Are Audible Files Saved as MP3?
Part 2. How to Change Audible from MP4 to AAX
Part 3. What to Do If You Cannot Find the File Extension
Part 4. How to Convert Audible Audiobooks to MP3 Format

What Happened to Audible Audiobooks Stored as MP4?

It appears that Firefox, the browser, is saving Audible titles as MP4 file. All those audiobooks are downloaded from the Library page of the Audible website. It is caused by the latest update of Firefox. So, if you've updated the browser to the latest version of Firefox V93.0, which was released on October 5, 2021, you would encounter the problem.


Then if you use Firefox V93.0 to download your liked titles from the Audible website, you'll find that all the downloads are going to saved as MP4 files. On the pop-up that prompts for saving Audible books as MP4 files, simply select Save File to download and save Audible books in MP4 format to your computer.

download audible from firefox

How to Change Audible Audiobooks from MP4 to AAX

Nothing is more frustrating than having your Audible books not work on your device. If your Audible downloads are stored as MP4 files and not working, try the following solutions to change Audible from MP4 to AAX.

Method 1. Change the file extension from MP4 to AAX

When those downloads initiated from the Audible website are saved as MP4 files, don't worry, and you still have the chance to get Audile AAX files by changing the file extension. In fact, all Audible titles exist in the format of AAX with digital rights management protection. So, no matter it is saved as MP4 or AAX, it is still AAX file. Then just follow the below steps to change the file extension from MP4 to AAX.

rename audible from firefox

If you are using a Mac computer,

1. Open Finder on your Mac then find the Audible downloads.
2. Right-click the Audible file and then choose Rename to change the file extension from .mp4 to .aax.

If you are using a PC computer,

1. Go to the Downloads folder from Firefox and then select the Audible file.
2. Right-click the file name and select Rename to change the file extension from .mp4 to .aax.

Method 2. Use another browser to download Audible titles

The first method is to manually rename the files from MP4 to AAX by changing the file extension. It will take a little time to get it done if you don't know how to do. The more direct way to fix it is to use other browsers such as Google Chrome to redownload your audiobooks from the Audible website again. Then those titles will be saved as the original AAX format.

download audible via google

What to Do If You Cannot Find the File Extension

The filename extension appears at the end of some filenames, and look like a period followed by a few letters or words. From the file's filename extension, you could know what type of file it is and what apps can open it. But sometimes, filename extensions are usually hidden in macOS and Windows. So if you want to change the Audible file's filename extension from MP4 to AAX, you should make them show on your computer first.

On Mac

1. In the Finder on your Mac, go to Finder > Preferences, then click Advanced.
2. Select "Show all filename extensions."

show filename on mac

On Windows

1. Click on the Windows Start button to open the File Explorer and then select the Explorer icon.
2. Click the View tab in File Explorer and then check the box next to File name extensions.

show filename on windows

How to Convert Audible Audiobooks to MP3

AAX is an unique audio file type that's slightly different from MP3, the universal file format. If you want to listen to Audible audiobooks on those portable devices not working with the Audible app, you might need to convert Audible to MP3 because of the former being the protected file format only playable within the Audible app. In order to convert Audible books to MP3 in the easiest way possible, all you'll require is ViWizard Audible AAX/AA Converter.

ViWizard Audible Audiobook Converter is an audio converting tool that is specially designed to handle the conversion of Audible audiobooks. Amongst many other formats, it supports MP3, M4A, AAC, AC3, OGG, AIFF, and other commonly-used audio formats. Then you could do the following steps to convert Audible to MP3 without degrading the audio quality.

spotify music converter

Best Audible AAXC to MP3 Converter Key Features

  • Convert all Audible audiobooks to plain formats like mp3
  • Remove protection from Audible audiobooks losslessly
  • Customize lots of audio parameters for output audiobooks
  • Split audiobooks into small segments by time or by chapters
Download Download

1Drag Audible books to the converter

Start by launching ViWizard Audible AAX/AA Converter on your computer then find the Audible downloads you want to convert. Then click the Add Files button to load the protected AA or AAX audiobooks from your computer. In addition, you can directly drag and drop the Audible files to the converter.

add audible aax files

2Configure the parameters for Audible

After the audiobook files are imported into the converter, click the Format panel at the bottom left of the converter interface. On the pop-up window, you could set the output audio format and just choose MP3 as the output format. To keep the original audio quality, go to adjust the codec, channel, sample rate, and bit rate.

set audiobook output formats as mp3

3Start to convert Audible books to MP3

If you want to split the audiobook into several segements, you could click the Edit icon at the rear of each book before starting the conversion. Then click the Convert button to start converting protected Audible books from AAX to MP3 at up to 100× faster speed. After completing the conversion, click the Converted button to see the Audible MP3 files.

converted mp3 audiobooks


If you get a bug alert that all the titles downloaded from the Audible website are saved as MP4 files, then follow the above solutions to resolve it. By the way, you could try using ViWizard Audible Audiobook Converter to convert your audiobooks to MP3 for playing anywhere.


is an experienced writer of ViWizard who is obsessed about tech, movie and software.

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