What Is ALAC? Apple Lossless Audio Explained

ALAC stands for Apple Lossless Audio Codec — a lossless audio compression format Apple developed in 2004 and open-sourced in 2011. ALAC compresses audio to roughly half the size of WAV while preserving every original sample exactly. It is Apple's answer to FLAC, and the technical comparison between the two is one of the longest-running debates in digital audio.

This guide explains exactly what ALAC is, how it differs from FLAC and WAV, when it sounds different (spoiler: it doesn't), what file extension it uses, how Apple Music uses it, and what the practical tradeoffs are.

The TL;DR

• ALAC is lossless. Compressing audio to ALAC and decoding it back produces a bit-perfect copy of the original. No data is discarded.
• ALAC files are 40-60% the size of WAV for the same audio content. Compression ratio depends on the source material — more complex audio compresses less.
• ALAC vs FLAC: identical audio quality. Both are lossless. Compression efficiency is roughly equivalent (FLAC is usually 1-5% smaller). The real difference is ecosystem support.
• ALAC files use the .m4a extension (or sometimes .alac). They are not the same as default AAC M4A files, which are lossy.
• Apple Music's "Lossless" tier streams ALAC at up to 24-bit/192 kHz.

What "Lossless" Actually Means

Lossless compression discards no audio data. When you decode an ALAC file, you get the original PCM samples bit-for-bit identical to the source. This is different from lossy formats (MP3, AAC, OGG, Opus) which permanently discard data the encoder estimates you won't notice.

Practically: an ALAC file converted back to WAV produces a WAV file that's byte-identical to the original WAV before compression. Same audio, smaller file. The format is reversible.

This is the same principle as FLAC, ALAC, and other lossless codecs. The technical approach differs (different prediction models, different entropy coding) but the result is the same: zero quality loss.

ALAC vs WAV

WAV stores raw PCM samples with no compression. A 4-minute song at CD quality (16-bit, 44.1 kHz, stereo) is roughly 42 MB.

ALAC compresses the same audio to 20-30 MB (typical for music). Approximately 50% smaller. The audio is bit-identical when decoded.

When to choose WAV over ALAC:

• DAW work — WAV has zero decode overhead. Plugins and audio software handle it natively without any codec layer.
• Maximum compatibility — WAV plays in every audio tool ever made. ALAC requires an Apple-aware decoder.
• Live editing and scrubbing — WAV's lack of compression makes random-access seeking instant.

When to choose ALAC over WAV:

• Storage efficiency — half the file size for the same audio.
• Apple ecosystem distribution — iTunes, Apple Music, iOS all decode ALAC natively.
• Archive collections — same audio quality as WAV at half the size.

ALAC vs FLAC

This is the question audiophiles love to argue about. The technical answer is: both are lossless, both produce identical audio when decoded. There is no sound quality difference whatsoever between an ALAC file and a FLAC file containing the same source audio. Both decode to bit-identical PCM.

The differences are practical:

| Attribute | ALAC | FLAC | |---|---|---| | Audio quality | Lossless | Lossless | | Typical compression | 50-60% of WAV | 50-55% of WAV (slightly smaller) | | Compression efficiency | ~1-5% larger than FLAC | Slight edge | | Apple devices native support | ✅ Yes | ⚠️ iOS 11+ files app yes; iTunes no | | Android native support | ⚠️ Android 5+ | ✅ Android 3.1+ | | Browser support | ⚠️ Limited | ⚠️ Limited | | Linux native support | ✅ Yes | ✅ Yes | | Open source | ✅ Yes (since 2011) | ✅ Always | | Metadata | MP4 atoms (rich) | Vorbis Comments (rich) | | File extension | .m4a (or .alac) | .flac |

For an Apple-centric library, ALAC is the natural choice — it plays everywhere your audio needs to play. For a cross-platform library or Android-centric setup, FLAC has slightly broader support and slightly better compression.

ALAC vs AAC (Lossy M4A)

This is where confusion often happens. Both ALAC and AAC commonly use the .m4a extension, but they're fundamentally different:

• ALAC is lossless — every sample preserved, file is large.
• AAC is lossy — data discarded for compression, file is small.

A 4-minute song:

• ALAC (.m4a): ~25 MB
• AAC (.m4a) at 256 kbps: ~7.7 MB
• AAC (.m4a) at 128 kbps: ~3.8 MB

You can usually tell them apart by file size (ALAC is much bigger) or by checking the file in iTunes/Music/Finder — the "Kind" field will say "Apple Lossless audio file" for ALAC and "AAC audio file" for lossy.

To explicitly convert from lossy AAC M4A to lossless ALAC: there's no point. The original AAC already discarded data. Converting to ALAC produces a larger file containing the decoded lossy audio — same quality as the AAC, just bigger. ALAC's benefit only matters when the source is itself lossless (WAV, FLAC, CD rip).

File Extension and Container

ALAC audio is almost always stored in an MP4 container with the .m4a extension. Less commonly, the .alac extension is used (some tools support it, others don't). Apple's official extension is .m4a — same as lossy AAC.

To tell whether an .m4a file is ALAC or AAC:

• macOS Finder: select the file, press ⌘I, look at "Kind" — "Apple Lossless audio file" = ALAC, "AAC audio file" = lossy AAC.
• iTunes / Music app: right-click → Get Info → File tab → check "Kind".
• Command line: `ffprobe file.m4a` and look for codec_name (alac vs aac).
• File size heuristic: ALAC is much larger than AAC for the same duration. A 4-minute song over ~15 MB is almost certainly ALAC.

Apple Music's ALAC Streaming

Apple Music added "Lossless" and "Hi-Res Lossless" tiers in 2021. The format used is ALAC:

• Lossless — ALAC at CD quality (16-bit/44.1 kHz)
• Hi-Res Lossless — ALAC at up to 24-bit/192 kHz (requires external DAC for full bit depth on most devices)

These tiers stream more data than the standard AAC tier (256 kbps), so they require more bandwidth and storage. Most listeners cannot reliably distinguish 256 kbps AAC from ALAC in blind tests at consumer playback levels — Apple's "Lossless" tier is more about peace of mind and audiophile preference than measurable audible improvement on typical hardware.

Apple's Hi-Res Lossless (24-bit/192 kHz) is a different beast — it preserves the full studio master quality, which matters for mastering workflows or critical listening on revealing playback chains, but is essentially indistinguishable from CD quality on consumer hardware.

When to Use ALAC

Apple ecosystem audio archive. If your music library lives in iTunes/Music and you want lossless quality, ALAC is the right choice — native support across all Apple devices.

Ripping CDs in an Apple environment. macOS Music app rips CDs to ALAC at the highest quality setting. No quality loss from the original CD, integrated library management.

iOS playback of lossless audio. Files in the iOS Files app, AirPods Max with wired connection, or any iPhone audio routing scenario where you want maximum quality.

Cross-codec collections. If you have a mix of FLAC and AAC files and want one lossless format for consistency, ALAC handles both lossless (matches FLAC quality) and integrates better than FLAC with Apple software.

When to Use FLAC Instead

Cross-platform libraries. FLAC has broader native support across Android, Linux, and pro audio software than ALAC.

Audiophile streaming services. Tidal HiFi, Qobuz, and most lossless streaming services use FLAC, not ALAC.

Open-source music management. Plex, Roon, MusicBee, foobar2000 — all handle FLAC excellently. ALAC support is good but FLAC is often the default.

Slight compression edge. FLAC compresses 1-5% smaller than ALAC on average. Marginal but real over a large library.

How to Convert Between ALAC, FLAC, and WAV

Converting between lossless formats (ALAC ↔ FLAC ↔ WAV) is always quality-preserving — every conversion preserves all original audio data. You're just changing the container/compression scheme.

For Apple-ecosystem use, convert FLAC or WAV files to ALAC to make them play natively in iTunes/Music without third-party plugins.

For cross-platform use, convert ALAC to FLAC for broader device support.

For DAW work, convert lossless audio (any format) to WAV for zero-decode-overhead editing.

AudioUtils handles common audio format conversions including AAC/M4A handling, but for ALAC specifically you may want to use Apple's Music app (Preferences → Files → Import Settings → Apple Lossless Encoder) or a tool like XLD on Mac.

Common Myths About ALAC

"ALAC sounds better than FLAC." No. Both are lossless. Both decode to bit-identical audio. There is no audible difference.

"ALAC is the same as AAC." No. AAC is lossy (data discarded), ALAC is lossless (no data discarded). Both can use the .m4a extension, which is the source of confusion.

"You can convert MP3 to ALAC for better quality." No. The MP3's quality ceiling was set when it was compressed. Converting to ALAC produces a larger file with the same (lossy) audio quality.

"ALAC is proprietary." No longer. Apple open-sourced ALAC in 2011 under the Apache 2.0 license. The reference codec is freely available; the format is documented and unencumbered.

"Apple Music streams MP3." No. Apple Music standard quality is AAC at 256 kbps. The Lossless tier streams ALAC at 16-bit/44.1 kHz. Hi-Res Lossless streams ALAC at up to 24-bit/192 kHz.

"ALAC files are huge." Compared to lossy AAC, yes — roughly 3-5× larger. Compared to WAV, ALAC is about half the size. It's smaller than uncompressed audio but bigger than lossy compressed audio.

Summary

ALAC (Apple Lossless Audio Codec) is a lossless audio compression format that produces bit-identical audio at roughly half the size of WAV. It's Apple's equivalent of FLAC — both are lossless, both produce identical audio quality, the difference is ecosystem support. For Apple-centric libraries, ALAC is the right lossless choice. For cross-platform setups, FLAC has broader support. Both store the same audio quality and decode to the same PCM — choose based on where your files need to play, not on imagined sound quality differences.