ALAC (Apple Lossless Audio Codec)
Apple's own lossless format that shrinks audio files without losing a single bit of the original sound.
| Full name | Apple Lossless Audio Codec |
| Extension | .m4a |
| MIME type | audio/mp4 |
| Developer | Apple |
| Released | 2004 (open-sourced October 2011) |
| Type | Lossless audio codec |
| Bit depth | 16, 20, 24, or 32 bits |
| Sample rate | 1 Hz to 384,000 Hz |
What is a ALAC file?
ALAC is a lossless audio codec made by Apple. It compresses audio files so they take up less space, but decoding gives back exactly the original data, bit for bit. It is built into every Apple device and platform.
ALAC stands for Apple Lossless Audio Codec. Unlike MP3 or AAC, it throws away no audio information during compression. A decoded ALAC file is identical to the source WAV or AIFF. The codec supports up to eight channels and bit depths up to 32 bits, so it handles everything from stereo music to multichannel recordings.
History
Apple introduced ALAC on April 28, 2004, bundled with iTunes and QuickTime as a proprietary format. It stayed closed for seven years until Apple open-sourced the encoder and decoder in October 2011 under the Apache License. Since then the reference code has lived on GitHub and the format has been adopted by third-party players and operating systems.
How it works
ALAC audio data sits inside an MPEG-4 container, which is why files carry the .m4a extension and the audio/mp4 MIME type. Inside the container, the codec uses linear prediction to model audio samples, then applies adaptive Rice coding to compress the residuals. This two-step approach gives compression ratios typically between 40 and 60 percent of the original PCM size while keeping the data fully reversible.
What it is used for
- Storing a music library in full quality on Apple devices and iTunes
- Archiving recordings where no audio quality can be sacrificed
- Streaming lossless audio through Apple Music
- Editing projects where source files must remain pristine between sessions
How to open it
On any Apple device, ALAC files open natively in the Music app, QuickTime Player, and iTunes. On Windows and Linux, players such as VLC, foobar2000, and ffmpeg all read ALAC without plugins.
Pros and cons
Strengths
- Zero quality loss compared to the original PCM audio
- Native support on all Apple devices and platforms with no extra software
- Open source under the Apache License since 2011
- Supports high-resolution audio up to 32-bit depth and 384 kHz sample rate
Trade-offs
- Files are larger than lossy formats like MP3 or AAC
- Less widely supported than FLAC on non-Apple hardware
- Not suitable when storage space or bandwidth is tight
- Metadata handling can vary between non-Apple players
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ALAC FAQ
Is ALAC the same as FLAC?
No. Both are lossless formats but they are different codecs. FLAC is an open standard maintained by the Xiph.Org Foundation. ALAC was created by Apple and uses an MP4 container, while FLAC uses its own container. Both decode to identical audio, so the difference is mainly compatibility and ecosystem.
Does converting ALAC to MP3 or AAC lose quality?
Yes. MP3 and AAC are lossy formats. Converting from ALAC to either one permanently removes audio data that cannot be recovered. If you need a lossy copy, keep the ALAC file as your master.
Why do ALAC files use the .m4a extension instead of something like .alac?
ALAC audio is stored inside an MPEG-4 container, the same container format used by AAC audio. Apple chose .m4a for both, so the extension does not tell you whether the audio inside is lossy or lossless. You have to check the codec in a media-info tool to be sure.
Can I play ALAC files on Android or Windows?
Yes. VLC supports ALAC on Android, Windows, and Linux. On Windows, foobar2000 also reads ALAC natively. Support is not as universal as FLAC, but most modern media players handle it without extra steps.