AIFF Format: The Complete Guide to Audio Interchange File Format

What Is AIFF?

AIFF stands for Audio Interchange File Format, a lossless audio container format developed by Apple and Electronic Arts in 1988. AIFF stores uncompressed PCM (Pulse-Code Modulation) audio data — the same raw digital audio representation used in professional recording studios, CD audio, and broadcast production.

AIFF was designed for the Macintosh and became the native audio format of macOS and professional Apple audio software (Logic Pro, GarageBand, Final Cut Pro). It is the Apple ecosystem's equivalent of WAV (which serves the same role on Windows). Today AIFF remains widely used in professional audio production, music mastering, and archiving workflows that demand lossless quality.

File Structure: Interchange File Format (IFF)

AIFF is built on the IFF (Interchange File Format) chunk structure, originally developed by Electronic Arts and Jerry Morrison for the Amiga computer in 1985. IFF organises data as a hierarchy of typed chunks:

FORM chunk (outer container)
  FORM size          (4 bytes, big-endian)
  AIFF identifier    ("AIFF" — 4 bytes)

  COMM chunk (required)
    numChannels      (2 bytes) — 1=mono, 2=stereo, 6=5.1
    numSampleFrames  (4 bytes) — total number of sample frames
    sampleSize       (2 bytes) — bits per sample (8, 16, 24, 32)
    sampleRate       (10 bytes) — 80-bit extended precision float (unusual!)

  SSND chunk (Sound Sample Data — required)
    offset           (4 bytes) — byte offset into block
    blockSize        (4 bytes) — block alignment size (0 for no alignment)
    soundData        (variable) — raw PCM audio samples

  MARK chunk (optional) — markers (cue points, loop start/end)
  INST chunk (optional) — instrument settings (used in samplers)
  MIDI chunk (optional) — MIDI data
  AESD chunk (optional) — audio recording information
  APPL chunk (optional) — application-specific data
  NAME chunk (optional) — name string
  AUTH chunk (optional) — author string
  (c)  chunk (optional) — copyright string
  ANNO chunk (optional) — annotation strings

Big-endian byte order: AIFF stores all multi-byte integers in big-endian (Motorola) byte order, reflecting its Macintosh/68000 origins. This contrasts with WAV, which uses little-endian (Intel) byte order.

Sample rate storage: The sampleRate field in the COMM chunk is stored as a 10-byte IEEE 754 80-bit extended precision floating-point number. This is unusual — most formats use a simple integer for sample rate. The extended precision accommodates rates like 44,100, 48,000, 88,200, 96,000, 176,400, and 192,000 Hz without loss.

Audio Data: PCM Format

The SSND chunk contains raw PCM audio samples:

• Bit depth: 8, 16, 24, or 32 bits per sample. 16-bit is CD quality; 24-bit is professional recording quality.
• Channels: Interleaved — for stereo, the samples alternate: L₁ R₁ L₂ R₂ L₃ R₃ ...
• Signed integers: Samples are signed two's complement integers (unlike WAV 8-bit which is unsigned).
• No header within SSND: The block data is raw samples without any internal framing.

File size formula:

File size ≈ (bit_depth / 8) × num_channels × sample_rate × duration_seconds

A 5-minute stereo 24-bit/96kHz AIFF:

= (24/8) × 2 × 96,000 × 300
= 3 × 2 × 96,000 × 300
= 172,800,000 bytes ≈ 165 MB

AIFF vs. AIFF-C (AIFC)

Apple also defined AIFF-C (Audio Interchange File Format Compressed), using the chunk type identifier AIFC instead of AIFF:

FORM chunk
  AIFC identifier    ("AIFC" instead of "AIFF")

  COMM chunk (extended for compression)
    ... same as AIFF COMM ...
    compressionType    (4 bytes) — codec identifier ('NONE', 'sowt', 'fl32', etc.)
    compressionName    (Pascal string) — human-readable codec name

Common AIFC compression types:

• NONE — uncompressed PCM (same as plain AIFF)
• sowt — little-endian PCM ("swapped" — same samples as WAV)
• fl32 — 32-bit IEEE 754 floating-point PCM
• fl64 — 64-bit IEEE 754 floating-point PCM
• alaw — G.711 A-law logarithmic compression (telephony)
• ulaw — G.711 μ-law logarithmic compression (telephony)
• MACE3 / MACE6 — Macintosh Audio Compression and Expansion (Apple proprietary)

The sowt (little-endian PCM) format is interesting because it is byte-for-byte identical to a WAV file's audio data — only the header structure differs.

AIFF vs. WAV vs. FLAC vs. ALAC

AIFF vs. WAV: The two formats are functionally equivalent — both store uncompressed PCM. The differences are byte order (big-endian vs. little-endian) and chunk container (IFF vs. RIFF). Any DAW (Digital Audio Workstation) can handle both. The choice typically reflects OS preference: macOS users default to AIFF; Windows users default to WAV.

AIFF vs. FLAC: Both are lossless, but FLAC applies lossless compression reducing files by 40-60%. FLAC is preferred for storage and distribution; AIFF/WAV are preferred in active DAW projects where disk bandwidth matters (compressed audio requires decompression on every read).

Professional Use Cases

Music mastering: Mastered audio is typically delivered as 24-bit/44.1kHz or 24-bit/96kHz AIFF or WAV. Many mastering engineers prefer AIFF on macOS-based workflows.

Sample libraries: Instrument samples in Native Instruments, EastWest, Spitfire Audio, and other professional sample libraries are distributed as 24-bit/96kHz AIFF or WAV.

Logic Pro / GarageBand: Apple's DAWs use AIFF as their native audio format for rendered tracks, bounces, and exported stems.

Broadcast and post-production: AIFF files (or broadcast WAV with BWF metadata) are the standard delivery format for audio in television and film post-production.

iTunes / Apple Music: The iTunes Store historically used AIFF for the highest-quality option before transitioning to Apple Lossless (ALAC).

Limitations

• No lossless compression: AIFF files are large. A 24-bit/96kHz stereo recording uses 3× more disk space than a 16-bit/44.1kHz WAV of the same duration.
• Limited metadata: AIFF lacks standardised ID3 or VorbisComment metadata. Some tools add metadata in the APPL chunk, but compatibility is inconsistent.
• Big-endian only: Original AIFF is big-endian; some older Windows tools may not handle it correctly (though modern tools handle both byte orders).
• No DRM: AIFF cannot carry DRM information. Protected Apple Music downloads use ALAC with FairPlay DRM, not AIFF.

Converting AIFF

AIFF → MP3: Lossy compression from lossless source. Use iTunes/Music app on macOS, Audacity, ffmpeg. Always convert from the lossless master; never convert MP3 to MP3 through AIFF.

AIFF → FLAC: Lossless-to-lossless transcode. FFmpeg: ffmpeg -i input.aiff output.flac. File size reduces ~50%. No quality loss.

AIFF → WAV: Functionally equivalent; just byte order conversion. FFmpeg: ffmpeg -i input.aiff output.wav. Useful for Windows compatibility.

AIFF → ALAC: Apple's lossless format in M4A container. iTunes/Music app on macOS handles this natively.

WAV/FLAC → AIFF: FFmpeg: ffmpeg -i input.wav output.aiff or ffmpeg -i input.flac output.aiff.

Summary

AIFF is a mature, professional-grade lossless audio format that occupies the same niche on macOS as WAV does on Windows. Its uncompressed PCM storage guarantees perfect audio fidelity with no generation loss through repeated open/save cycles — essential for professional music production and mastering. Its IFF chunk architecture is well-defined, its 80-bit sample rate field handles any professional sample rate without approximation, and its Apple ecosystem integration makes it the natural choice for Logic Pro users. For archiving, FLAC is more storage-efficient; for cross-platform compatibility, WAV is more universally supported; for Apple-centric workflows, AIFF remains the standard.

Related conversions

Audio format pairs that come up most often:

• M4A to MP3
• WAV to MP3
• FLAC to MP3
• AAC to MP3
• OGG to MP3
• MP3 to WAV