Convert M4A to MP3
M4A is Apple's audio-in-MP4 filename - what iTunes wrote for every song you ripped, bought, or synced through the 2000s and 2010s. Audio inside is AAC (default) or ALAC (Apple Lossless) - the extension is the same but the codec matters (see Audio codecs explained). Wave decodes either and re-encodes to a portable MP3 through libmp3lame at 192 kbps.
What actually changes
An M4A file is an MP4 container carrying an audio-only track. Apple introduced the .m4a extension in iTunes 4.5 (2004) to distinguish audio-only MP4s from video-only ones (.m4v), even though the underlying byte format is identical. The audio inside is almost always AAC-LC (Low Complexity, iTunes's default rip and purchase format from 2003 onward) or occasionally ALAC (Apple Lossless, added in iTunes 4.5, used for lossless CD rips). Wave decodes both through the ffmpeg-wasm engine.
AAC to MP3 is always a re-encode: the codecs are different, the compression models are different, and there's no bit-copy shortcut. Wave hands PCM samples from the AAC decoder to libmp3lame at 192 kbps VBR (LAME -q:a 2). At that target, on any consumer playback chain, the MP3 sounds identical to the AAC source. The efficiency gap AAC has at low bitrates (128 kbps and below) closes to nothing at 192 kbps and above.
For ALAC (Apple Lossless) sources, the decode is bit-exact - every sample the encoder wrote is recovered. LAME then encodes to MP3 at 192 kbps VBR, which is transparent on any consumer playback. If you're starting from an ALAC source and need a lossless target, keep the .m4a; if you need cross-device MP3 compatibility, the conversion is the right call.
The volume of M4A files in the wild is enormous. iTunes was the world's largest music retailer from 2008 to 2013; every song purchased from it landed as an M4A with AAC audio. Every song ripped from a CD through iTunes with the default settings also landed as an M4A. Apple Music's downloaded tracks (before 2022) are M4A with FairPlay DRM; post-2009 purchases and Apple Music's current downloadable format are DRM-free AAC in M4A. If you have any music library from an iPhone / iPod / Mac ecosystem, chances are much of it is M4A.
Three steps.
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Step 1
Drop the .m4a file onto the card.
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Step 2
Wave inspects the container and picks AAC or ALAC decoder accordingly.
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Step 3
Convert. Save the MP3.
Answers, specifically.
iTunes-purchased M4A - is it protected?
iTunes Music has been DRM-free since 2009 (labelled "iTunes Plus AAC"). Pre-2009 music purchases and rentals carry FairPlay DRM; Wave cannot decrypt those. Music you ripped from a CD, or purchased after 2009, converts without issue.
ALAC (Apple Lossless) M4A?
Yes. Wave decodes ALAC losslessly to PCM, then LAME encodes to MP3. The MP3 is lossy (as MP3 always is), but at 192 kbps VBR the result is transparent on any consumer playback.
Do iTunes metadata tags (title, artist, album art) carry over?
Title, artist, album, track number, year, and genre transfer to the MP3's ID3v2 frame. Album art doesn't transfer through the current pipeline - use a desktop tag editor if you need the artwork.
HE-AAC in M4A?
Yes. Some low-bitrate M4As (radio-station downloads, older podcast enclosures) use HE-AAC. All variants decode.
Apple Music downloads?
DRM-free Apple Music downloads (available since 2022) convert normally. DRM-protected downloads cannot be decoded outside Apple's ecosystem.
Podcast episodes ripped as M4A?
Yes. Podcast enclosures on Apple Podcasts and older RSS feeds sometimes shipped as M4A with AAC audio. The conversion preserves the whole episode's content.
Multi-language or chapter-marked M4A?
Wave takes the default-flagged audio track. Chapter marks (M4B audiobook style) are preserved as they can carry through the MP3 container; per-track extraction is on the roadmap.