Castos
Free Podcast Tool

Convert Audio To MP3

Convert MP3, WAV, M4A, AAC, OGG, or FLAC to a podcast-ready MP3. Free, private, and entirely in your browser.

Your audio stays on your device. Nothing is uploaded or stored.

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How To Convert Audio To MP3

  1. Step 1

    Choose Your Audio

    Select a MP3, WAV, M4A, AAC, OGG, or FLAC file from your device. The file stays in your browser and is never uploaded.

  2. Step 2

    Review The File

    Preview the audio and confirm it's the right one before converting. There's nothing else to configure.

  3. Step 3

    Convert And Download

    Click Convert To MP3 and download a podcast-ready file. The export is fixed at 128 kbps for clear spoken audio and a practical file size.

When You Need A Different Format

A voice memo comes off your phone as M4A. A recording booth exports WAV. A field recorder saves FLAC. Most podcast hosts, editors, and listening apps expect MP3, so the file you have often isn't the file you need. This tool handles that conversion without installing anything or creating an account.

Nothing Leaves Your Device

Most online converters upload your file to a server before they can return anything. This tool loads the converter into your browser instead, so an unreleased interview or a private recording never has to leave your computer. Close the tab and the working files disappear.

Podcast-Ready MP3 At 128 kbps

Every converted file is exported as an MP3 at 128 kbps, a standard podcast bitrate that keeps spoken audio clear at a practical file size. There is no format menu to configure and no extra setting to second-guess before you upload it to a host.

Audio Ready? Publish Your Podcast In 3 Steps

  1. Upload a new episode in Castos

    Upload The MP3

    Create a show in Castos and upload the converted MP3 with your episode title, description, and artwork.

  2. Fill in podcast details in Castos

    Get Your Feed And Website

    Castos creates the RSS feed podcast apps need and a customizable site where listeners can find every episode.

  3. Link your feed to each podcast directory

    Publish Everywhere

    Submit your feed to Apple Podcasts, Spotify, and other directories once. Future episodes are distributed automatically.

Frequently Asked Questions

How do I convert an audio file to MP3?
Choose a MP3, WAV, M4A, AAC, OGG, or FLAC file above and click Convert To MP3. Your browser creates a 128 kbps MP3 you can preview and download, no editing software or account required.
Is this audio converter free?
Yes. This converter is free, requires no account, and adds no watermark. The output is a standard 128 kbps MP3.
Is my audio file uploaded anywhere?
No. Your browser converts the file on your device with WebAssembly. Castos never receives or stores the source file or the converted MP3. The first conversion may take a moment because the browser needs to load the converter first.
Which audio formats can I convert?
The tool accepts MP3, WAV, M4A, AAC, OGG, and FLAC files up to 500 MB. Browser codec support can vary, so exporting an unusual file as WAV first is the best fallback.
Why is the output always 128 kbps?
128 kbps is a standard podcast bitrate. It keeps spoken audio clear at a practical file size for hosting and listening, so there is no format menu to configure or second-guess.
Can I convert a video file with this tool?
No, this converter is for audio files only. To pull the audio out of a video first, use the Extract Audio From Video tool, then convert the result here if you need a different format.

Publish Your Converted Audio With Castos

Upload your MP3, create your podcast feed, and distribute every episode from one place.

Get Started For Free