What audio and video files can I upload?
You can upload MP3, M4A, WAV or AIFF audio up to 2 GB, and MP4 or MOV video up to 30 GB if video is turned on for your podcast. MP3 is the preferred audio format.
Which formats can I upload?
- Audio: MP3, M4A, WAV and AIFF
- Video: MP4 and MOV, if video is enabled for your podcast
MP3 is the preferred audio format.
How large can my file be?
- Audio: up to 2 GB
- Video: up to 30 GB, or 5 GB through the API and MCP server
The uploader on the episode page shows the limit for your podcast.
Even though you can upload large audio files, we recommend keeping episodes under about 200 MB. Many listeners download episodes to their phones, and large files use up their data and storage. We've seen listeners unsubscribe from shows whose files are too big.
What settings should I use?
For audio, we recommend:
- Format: MP3
- Sample rate: 44.1 kHz (44100 Hz)
- Bit rate: around 128 kbps, constant bit rate (CBR)
- Loudness: -16 LUFS. See How loud should my podcast audio be?
Why constant bit rate?
Constant bit rate (CBR) MP3s use the same amount of data for every second of audio. Variable bit rate (VBR) MP3s use more data for complex sections and less for simple ones.
VBR files upload and play fine, but CBR is more reliable:
- Skipping ahead: some podcast apps skip to slightly the wrong point in a VBR file or show the wrong episode length
- Dynamic ads: if you use Campaigns, VBR audio can make ads play a second or two away from where you set them
Most editing software has a CBR or "constant" option in its MP3 export settings.
What happens to my file after I upload it?
When you upload your audio files to Transistor, we won't change your ID3 tags or downsample your audio.
If your file doesn't have ID3 tags, we will add them for you when you upload. If they aren't already present, we add ID3 tags for:
- Episode Title
- Podcast Title
- Author
- Publishing Year
- Episode Number
If you upload an M4A, WAV or AIFF file, we'll convert it to MP3 for you after you upload it. If you upload an MP4 or MOV video file, we'll extract the audio from it as an MP3 file.
If you upload an MP3 file, we don't perform any conversion. If your MP3 file includes chapter markers, we keep them in the file for your listeners.
If you have additional questions please reach out to us:
- Email - support@transistor.fm
- Live Chat: https://transistor.fm/contact/
Updated on: 04/11/2026
Thank you!