Finding the Right Audio File Format for your Podcast

If you’re reading this article, chances are you are at the last stage of your podcast recording process where you are required to export your audio file for publishing. You’ve probably noticed audio file format extensions like mp3, wav, aac, flac, and aiff. What these file types mean for audio quality, encoding, and publishing is what we will attempt to drill down in this article. Let’s take a look at an intro to these file types and some of the pros and cons of each.

MP3 files

If you have any base knowledge of digital audio, it’s likely that the mp3 format is the most familiar to you. That’s because it’s the most universal audio file format there is. This means that basically every audio player on the planet can support this file type. However, what the mp3 has in universality, it lacks in audio quality. That’s because in order for the mp3 to maintain its small file size, it has to be presented in a compressed format. That’s to say that you will sacrifice audio quality (lower bitrate) in order to have a smaller file size. If you are publishing your show to any of the main podcast listening apps like Apple Podcasts or Spotify (through a podcast hosting platform like Acast) mp3 format will be your best bet. We recommend compressing your show to 128 - 160kbps MP3 files as this is the size at which it will load quickly and any loss in audio quality will be unnoticeable. Your editing software should be able to export this file size, but if it doesn’t, you can use the free program Audacity to convert your file to mp3 format.

M4A files (aac)

M4A files have become increasingly common in recent years with many believing that it will be the format which ultimately replaces the mp3. The advantages of this format is that, while it is still a compressed format, it has a smaller file size while sacrificing less audio quality than an mp3. However, while the m4a is common on platforms like Apple Music (formerly iTunes), it lacks in compatibility and is not as universally accepted on Android and iOS streaming platforms. Be sure to check the specifications of your podcast platform before submitting an m4a file. (Note: Acast supports m4a file types.)

WAV files

You may be familiar with wav files as being the raw audio file you may encounter on a CD. wav files are typically uncompressed with extremely high sound quality. This, of course, means that the wav format ends up being too large for most web players. WAVs are ideal for listening and editing your podcast at home in high-quality, but should be converted to a different audio format before publishing.

FLAC files

While flac has yet to have it’s real moment in the sun, more platforms are beginning to adopt this format. That’s because flac presents audio in an uncompressed format and sacrifices very little audio quality in the process. If you are keeping a digital archive of your podcast episodes, flac is an ideal format because it will preserve your episodes with a small amount of disc space and no lossy compression.

What are the limits?

Most people use the Apple Podcasts app to listen to podcasts. Apple has set the file limit to 150MB for all files downloaded over a cellular connection (including apps, ebooks, and videos). When your listeners try to play your episode, they are greeted with a pretty unhelpful message—"episode unavailable"—which is a frustrating experience to say the least. To help our podcasters avoid this issue, Acast sets the internal limit to 150MB also.

To make your file smaller, use your audio editing software (like Garageband or Audacity) to export the episode audio file at a lower bitrate. Choose to export at 128kbps MP3.

What is the best audio file format for podcasting

An mp3 between 128kbp and 160kbps will be the best option for exporting your podcast as it maintains a small file size optimal for streaming while maintaining the integrity of the audio. Also, this format is supported by all major podcast platforms and networks (Acast included). 

Making sure your audio reaches your audience’s ears in high quality is an essential component for running a successful podcast. Optimizing your show for playback using the above audio recording and podcast editing methods will ensure that you end up with high quality audio for every episode.