Convert ALAC to MP3
ALAC (Apple Lossless Audio Codec) is Apple's FLAC equivalent - lossless compression, bit-exact reversible, half the size of WAV. Wave decodes ALAC in your browser and re-encodes to a portable MP3 through libmp3lame at 192 kbps. Audio codecs explained covers where ALAC sits vs. FLAC, MP3, and the rest.
What actually changes
ALAC was introduced by Apple in 2004 as their in-house alternative to FLAC, with a compression ratio comparable to FLAC and better integration into iTunes / macOS workflows. Apple open-sourced ALAC in 2011, and it's now decodable everywhere through libavcodec, libALAC, and Xiph.Org's reference decoder. ALAC files usually live inside an M4A container (Apple's MP4 for audio), so .m4a is the extension you'll see for most ALAC content; a small share of ALAC content ships in .caf (Apple Core Audio Format) containers or as bare ALAC bitstreams.
Wave decodes ALAC through ffmpeg-wasm's ALAC decoder (which produces bit-exact PCM samples - lossless) and re-encodes to MP3 at 192 kbps VBR through libmp3lame. The bit-exact decode means the LAME encoder sees exactly the samples the original PCM master carried; the resulting MP3 at 192 kbps is transparent on any consumer playback chain. Anything audible in the ALAC source is present in the MP3.
The typical ALAC source is a CD ripped through iTunes with the "Import Using: Apple Lossless" setting, or a high-resolution audio purchase from Apple's music store (2017 onward, when Apple started offering ALAC downloads for select audiophile content). Both use 16-bit / 44.1 kHz for CD-quality material and 24-bit / 96 or 192 kHz for high-resolution content. Wave handles all bit depths and sample rates.
ALAC and FLAC are functionally equivalent for the user's purpose - both are lossless, both compress to roughly 50-60% of the equivalent WAV size, both decode bit-exact. The difference is entirely ecosystem: ALAC works natively in iTunes / Music / macOS, FLAC works everywhere else. For an MP3 delivery target, either source produces the same-quality MP3. If you're starting from an ALAC library and want to move to a portable format, the conversion is straightforward and non-destructive - the ALAC source can stay in place.
Three steps.
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Step 1
Drop the .m4a (ALAC) or .caf file onto the card.
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Step 2
Wave inspects the container and picks the ALAC decoder.
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Step 3
Convert. Save the MP3.
Answers, specifically.
Is my .m4a ALAC or AAC?
Wave inspects the audio codec inside the M4A container and picks the right decoder either way. If you want to check ahead of time, iTunes shows codec info in a file's Get Info panel.
Is the MP3 lossless like the ALAC?
No - MP3 is a lossy codec by definition. But at 192 kbps VBR through LAME, the output is transparent on any consumer playback. If lossless-target is required, keep the ALAC or convert to FLAC through a desktop tool.
How much smaller is the MP3?
The MP3 is typically 30-40% of the ALAC's size. A 30 MB ALAC track becomes about a 9-10 MB MP3.
High-resolution ALAC (24-bit 96 kHz)?
Yes. Wave decodes at native precision; LAME encodes to MP3 at 192 kbps VBR. Extra bit depth and sample rate don't translate into audible improvements on consumer gear, so the MP3 preserves everything reproducible.
Do iTunes tags carry over?
Title, artist, album, track number, year, and genre transfer to ID3v2. Album art doesn't transfer through the current pipeline.
DRM-protected ALAC?
Music purchased from iTunes has been DRM-free since 2009. Pre-2009 music purchases and rentals carry FairPlay DRM; Wave cannot decrypt those.
Bare ALAC bitstream (no container)?
Wave handles ALAC inside M4A and CAF. Truly-bare ALAC bitstreams outside a container are rare; if you have one, wrap it in an M4A with a desktop tool first.