How to convert M4A to MP3 on a Mac without uploading
By Himanshu Ranjan · Updated 8 November 2026
Select the M4A files in Finder, open FileDial, and run Convert › Convert to MP3. Each file gets a new MP3 copy beside the original, and nothing is uploaded. For a one-off you can also use the Music app: set Import Using to MP3 Encoder, then choose File › Convert › Create MP3 Version.
M4A and MP3 are different kinds of file
M4A is usually AAC audio stored in an MP4 container. MP3 is an older, very widely supported lossy format. Apple devices and apps handle M4A without trouble, but some car stereos, older players, editing tools and web forms still ask for MP3.
Both formats are lossy, so a conversion between them is a second round of lossy compression. The audio will not become better, and a heavily compressed M4A can pick up extra artifacts as an MP3. Keep the original M4A if it matters, which is why FileDial always saves a copy instead of replacing it.
Convert M4A to MP3 with FileDial
FileDial works from Finder, so there is no import step and no library to manage. You can select one file or a whole folder's worth.
- Select one or more .m4a files in Finder.
- Hold the right Option key to open the dial (or use the shortcut you set in Settings).
- Choose Convert › Convert to MP3 and release on it.
- Find the new .mp3 beside each original. The result card shows what was made, and Undo removes the new file if you change your mind.
Doing a whole folder at once
Because FileDial runs one tool on every selected file, converting a folder of M4A recordings is the same four steps. Select everything in the folder with Command-A, then run the same tool. If you get new M4A files regularly, a watched folder can run a recipe on anything you drop into it.
Rename the results with Rename › Rename with pattern… if the MP3 names need a date or sequence number. Renaming changes originals, so run it on the converted copies.
The built-in macOS way: the Music app
The Music app can create an MP3 version of a song in your library. In Music, open Music › Settings, click Files, then Import Settings, and set Import Using to MP3 Encoder. Select the songs, then choose File › Convert › Create MP3 Version. Apple notes that converting between compressed formats may reduce quality.
This works well for songs already in your library. It is less handy for loose recordings, because the files have to be added to Music first, and the converted copy lands in the library rather than next to the original file in Finder.
Why convert on your own Mac
Free web converters need you to upload the file, and the FBI Denver field office warned in March 2025 that free online converter tools are increasingly used to spread malware. Audio is often personal: interviews, voicemail, family recordings. FileDial runs every tool on your Mac and never uploads a file, and all tools work with Wi-Fi off.
M4A is not always the same audio inside
The .m4a extension is a container habit rather than a codec guarantee. Most M4A files hold AAC, but Apple Lossless audio also commonly uses the same extension. A lossless M4A converted to MP3 loses more than an AAC one does, because you are going from exact audio to lossy audio rather than lossy to lossy. If you want to keep exact quality and only need a smaller file, Convert › Convert to FLAC or Convert › Convert to Apple Lossless are options in the same menu.
Protected files are a separate problem. Apple says that you can convert iTunes Store purchases only if they are iTunes Plus songs, so older copy-protected purchases cannot be converted by any tool that respects the protection.
AAC versus MP3 in plain terms
AAC was designed as MP3's successor and generally achieves higher sound quality than MP3 at the same bit rate, according to the Wikipedia article on the format. The practical meaning is that an M4A and an MP3 of the same size usually favor the M4A. People convert to MP3 for reach, not for quality: MP3 is described as a de facto standard for digital audio with near-universal hardware and software support.
That is a good reason to convert exactly when you must, such as a car stereo, a podcast host that wants MP3, or an old phone, and a poor reason to convert a whole library for no reason.
Tidy up the results
Converted files keep working better when they are named and tagged properly. Tags › Edit tags… makes a new copy with the title, artist and album you enter, and fields you leave empty keep what is already there. If you plan to share the MP3 publicly, Tags › Remove tags makes a copy with the tags stripped. Rename › Add date prefix or Rename › Rename with pattern… help when a pile of recordings all have names like Recording 14. Those rename tools change the originals, and Undo puts the names back.
When not to convert
If the destination accepts M4A, leave it alone. If you need maximum quality for editing, convert to a lossless format instead, and see the lossless versus lossy explainer for the trade-off.
Questions
Will converting M4A to MP3 lose quality?
Slightly, yes. Both formats are lossy, so the audio is compressed a second time. For speech and casual listening the difference is usually small, but keep the original M4A if you may need it later. FileDial saves the MP3 as a new file and leaves the M4A untouched. Expect the MP3 to be slightly worse than the M4A at the same size, because AAC is generally the more efficient codec.
Can I convert many M4A files at once on a Mac?
Yes. Select all the files in Finder and run Convert › Convert to MP3 once. FileDial processes the whole selection and saves an MP3 beside each file. The Music app can also convert several songs at once, but only songs that are in your Music library. The tool treats each file independently, so a mixed folder of recordings and songs converts in the same pass, and any file that cannot be read is simply left without a result.
Does FileDial need an internet connection to convert audio?
No. Every tool runs on the Mac and files are never uploaded, so conversion works with Wi-Fi off. The app only goes online for the licence check and optional anonymous usage counts, which can be switched off in Settings. That means a flight or a basement is no obstacle, and nothing about the audio, its name or its location is sent anywhere during conversion.
Is there a free way to do this on a Mac?
Yes, the Music app can create MP3 versions once the import setting is MP3 Encoder. FileDial has a 1-day free trial with every tool, then costs $20 once, so you can try the Finder workflow before deciding. The paid app is worth it mainly if you convert often or in folders, since the Music route is fine for the occasional library song.