Apple Lossless Audio Codec
The Apple Lossless Audio Codec (ALAC) is a lossless digital audio compression format developed by Apple Inc., designed to reduce the size of audio files while preserving every bit of the original uncompressed data for exact reconstruction upon decoding.[1] Introduced on April 28, 2004, alongside iTunes 4.5 and QuickTime 6.5.1, ALAC was created as an efficient alternative to uncompressed formats like WAV and AIFF, enabling high-fidelity audio storage and playback within Apple's ecosystem without any loss in quality.[2][3] ALAC files are stored within an MP4 container (with the .m4a extension) and support a wide range of bit depths and sample rates, from standard CD quality at 16-bit/44.1 kHz to high-resolution audio up to 24-bit/192 kHz, making it suitable for professional and consumer applications alike.[1] It is natively integrated into Apple's hardware and software, including the Music app (formerly iTunes), iOS, macOS, iPadOS, and Apple Music, where the entire streaming catalog—over 100 million songs as of 2025—is encoded using ALAC to deliver lossless playback when enabled by users.[4][5][6] In October 2011, Apple released the ALAC specification and source code as an open-source project under the Apache License 2.0, broadening its adoption beyond proprietary use and allowing integration into third-party software and devices.[3]Introduction
Definition and Purpose
The Apple Lossless Audio Codec (ALAC) is an audio compression format developed by Apple Inc. for encoding digital audio files without any loss of data, ensuring that the decompressed output is identical to the original uncompressed audio.[1] Unlike lossy formats such as Apple's Advanced Audio Coding (AAC), which discard certain audio data to achieve smaller file sizes and thereby introduce irreversible quality degradation, ALAC retains 100% of the original audio information, making it ideal for audiophiles and professionals seeking bit-perfect reproduction.[4] The primary purpose of ALAC is to enable efficient storage and playback of high-fidelity audio while maintaining compact file sizes, particularly for managing extensive music libraries on devices with limited storage.[1] This allows users to preserve the full dynamic range and detail of source material, such as CD-quality recordings, without compromising sonic integrity during compression or transmission. Initially designed to support seamless integration within Apple's digital music ecosystem, ALAC facilitates high-quality archiving and sharing of audio content.[4] Developed as part of Apple's QuickTime multimedia framework in the early 2000s, ALAC was created to address the need for a lossless alternative to uncompressed formats like PCM, which require significantly more storage space.[7] ALAC files typically achieve compression ratios of 40-60% compared to uncompressed PCM audio, depending on the complexity of the source material, thereby reducing file sizes by approximately half on average while preserving every bit of the original data.Key Features and Benefits
ALAC distinguishes itself through its support for multi-channel audio configurations up to 8 channels, accommodating formats like stereo, 5.1 surround, and 7.1 immersive audio for enhanced listening experiences.[8] It also enables metadata embedding, including tags for artist, album, genre, and cover art, within its structure to maintain organized libraries without additional files.[9] Furthermore, ALAC integrates seamlessly with MPEG-4 containers under the .m4a file extension, promoting compatibility across media players and streaming services while preserving file portability.[1] The codec's primary benefits stem from its lossless compression, which reduces file sizes by roughly 40-60% compared to uncompressed PCM formats like WAV, without any degradation in audio fidelity, making it particularly suitable for archiving high-resolution music collections and enabling efficient portable playback on storage-constrained devices.[10] This preservation of bit-perfect quality aligns with ALAC's purpose as a lossless preservation tool. Additionally, its native optimization for Apple hardware ensures energy-efficient decoding, minimizing battery drain during extended playback on iOS and macOS devices.[1] Compared to FLAC, another prominent lossless codec, ALAC shares similar compression efficiency but offers distinct advantages in the Apple ecosystem:| Aspect | ALAC | FLAC |
|---|---|---|
| Licensing | Proprietary originally; open-source since 2011 under Apache License | Open-source from inception (BSD-like) |
| Native Integration | Optimized for Apple devices and silicon | Broad cross-platform support |
| Compression Performance | Comparable ratios; slightly larger files in some cases | Marginally more efficient in benchmarks |