Free tool

AAC to MP3 Converter

A .aac file holds AAC sound without the M4A wrapper, and some players, editors and older devices refuse it. Convert it to MP3 in a few seconds, right in this tab.

01 — Your file

Choose a file

02 — Result

Your converted file

Choose a file and press Convert to MP3. The conversion runs in this tab, so even large files never leave your computer or phone.

Steps to convert AAC to MP3

  1. Open the .aac file with the box above.
  2. Choose a bitrate at or a little above the file's own, which the file card shows.
  3. Convert and download the MP3.

Raw AAC versus M4A

AAC is the codec behind most phone, streaming and video audio. Usually it lives inside an MP4-family file such as .m4a or .mp4. A .aac file is the same sound written as a raw stream of frames, a format called ADTS, with no container around it. Raw AAC comes from some voice recorder and call recorder apps, from recordings of internet radio, and from tools that extract a video's soundtrack without rewrapping it.

The raw format has no index. That has one visible effect here: the length the file card shows is estimated from the bitrate and may be a little off. The conversion itself always processes the whole file.

Matching the bitrate

AAC is more efficient than MP3, so an MP3 needs a somewhat higher bitrate to sound as good. A 128 kbps AAC file converts well at 192 kbps MP3, and a 256 kbps AAC file at 320 kbps. Going higher than that only makes the file bigger. For speech recordings, 128 kbps is enough whatever the source.

When you don't need MP3

If your app accepts M4A, the audio converter can copy the AAC sound into an M4A without re-encoding at all, which is instant and lossless. That is often the better fix for Apple devices. The AAC vs MP3 comparison explains where each format wins.

Transcribing an AAC recording

mydubly's audio to text tool accepts AAC files directly and returns a timestamped transcript, so a call or voice recording in .aac can be transcribed as it is.

How the free converter works

The converter is ffmpeg, the open-source media toolkit, compiled to WebAssembly so it runs inside your browser tab. Your file is read straight from your disk by that engine; it is never uploaded to mydubly or anywhere else, and no account is needed.

  • The engine is about 30 MB and downloads the first time you convert something. After that your browser normally keeps it.
  • Large inputs are fine because the file is read in place, but the result is built in memory, so outputs are capped at about 1.5 GB.
  • Speed depends on your device. Copying streams takes seconds; re-encoding video is the slow case.
  • Keep the tab open until the download button appears. Closing it stops the conversion.

More free tools

Turn the file into text

Frequently asked questions

Why does the length of my AAC file look wrong?

Raw .aac files have no index, so the length is estimated from the bitrate. The converted MP3 has the correct length.

Is AAC better than MP3?

At the same bitrate AAC usually sounds better. MP3's advantage is that every device and app plays it.

Can I convert AAC to M4A without losing quality?

Yes. Choose M4A on the audio converter and the AAC sound is copied without re-encoding.

Does AAC to MP3 work on Android?

Yes, in current Chrome, Firefox and Samsung Internet. Choose the file from your recordings or Files app.