AIFF (Audio Interchange File Format) is an uncompressed audio container that stores linear PCM samples in big-endian byte order, wrapped in a structure of labeled data blocks called chunks. Among audio formats & codecs, it plays the same role as WAV: a lossless, edit-friendly file for recording, production, sample libraries and the exchange of masters between studios and applications.
AIFF was introduced by a computer manufacturer in the late 1980s and is built on an earlier general-purpose container, the Interchange File Format. It remains the traditional native uncompressed format on macOS, and all major digital audio workstations, editors and players read it.
How an AIFF file is structured
Every AIFF file is a single FORM chunk whose type field reads AIFF, and inside it sit smaller chunks, each with a four-character identifier, a 32-bit length and its data. A reader can skip chunks it does not understand, which makes the format extensible without breaking older software.
Two chunks are mandatory for audio. The Common chunk (COMM) describes the stream, and the Sound Data chunk (SSND) holds the samples themselves. Further chunks carry markers, loop points, comments or tag metadata, as the table below shows.
| Chunk | Purpose | Required |
|---|---|---|
| FORM | Outer container with the AIFF or AIFC type | Yes |
| COMM | Channels, frame count, bit depth and sample rate | Yes |
| SSND | Interleaved sample frames with an alignment offset | Yes, when audio is present |
| MARK | Named positions in the audio | No |
| INST | Base note, key range and sustain or release loops | No |
| ID3, NAME, AUTH, ANNO | Title, artist, comments and other tags | No |
A distinctive detail is that the COMM chunk stores the sample rate as an 80-bit extended-precision floating-point number. Software that parses AIFF by hand must convert this value correctly, or it will report wrong sample rates.
Audio parameters an AIFF file can hold
Standard AIFF holds uncompressed integer PCM at practically any common resolution and rate. Because no data is discarded, the file size follows directly from sample rate times bit depth times channel count, which makes the format predictable but large.
The COMM chunk allows sample sizes from 1 to 32 bits, and in practice files use 8, 16, 24 or 32-bit integer samples. Samples narrower than a full byte boundary are padded and left-justified, so a 20-bit recording occupies three bytes per sample. Channel counts are not limited to stereo; multichannel AIFF files interleave each sample frame across all channels in a fixed order.
| Configuration | Typical use | Approximate size per minute |
|---|---|---|
| 44.1 kHz, 16-bit, stereo | CD-quality masters and samples | About 10 MB |
| 48 kHz, 24-bit, stereo | Video and broadcast production | About 17 MB |
| 96 kHz, 24-bit, stereo | High-resolution recording | About 35 MB |
| 48 kHz, 24-bit, mono | Single-track recording stems | About 8.6 MB |
The 32-bit length fields impose a practical limit of about 4 GB per file, which equals roughly 3 hours and 20 minutes of 48 kHz, 24-bit stereo. Long multichannel recordings therefore need splitting or a container with 64-bit sizes.
AIFF-C and compressed variants
AIFF-C (AIFC) is the extended version of the format, which adds a compression type field to the COMM chunk. Despite its name, it is often used without any data reduction: the most common AIFF-C files simply store little-endian or floating-point PCM.
- NONE: big-endian PCM, identical in content to plain AIFF.
- sowt: little-endian PCM, which some applications write for speed on Intel and ARM processors.
- fl32 and fl64: 32-bit or 64-bit floating-point samples for processing headroom.
- ulaw, alaw and ima4: legacy telephone and ADPCM codecs with lossy reduction.
Support for the variants is uneven. A player that handles plain AIFF may reject an AIFF-C file with an unusual compression code, so exchange files are safest as plain big-endian integer PCM.
AIFF compared with WAV, FLAC and ALAC
AIFF is closest to WAV: both carry the same uncompressed PCM audio and differ mainly in byte order and metadata conventions. Converting between them is lossless, while lossless codecs such as FLAC and ALAC reduce file size without changing a single sample.
| Format | Compression | Byte order | Main strength |
|---|---|---|---|
| AIFF | None in standard form | Big-endian | Simple, edit-ready, strong tagging support |
| WAV | None in standard form | Little-endian | Universal production and broadcast default |
| FLAC | Lossless, roughly 40 to 60 percent of original size | Not applicable | Open, efficient archival and distribution |
| ALAC | Lossless, similar ratio to FLAC | Not applicable | Native lossless in Apple ecosystems |
In practice, the choice between AIFF and WAV is rarely about sound, because the audio is bit-identical. It is about tool compatibility and metadata: AIFF has long supported embedded ID3 tags and artwork in music libraries, whereas WAV is preferred in broadcast workflows that rely on its own metadata extensions.
When to use AIFF and what to avoid
AIFF suits any stage where audio is still being edited or exchanged at full quality: recording, sample libraries with loop points, stem delivery and archive copies of finished masters. For listening and distribution, a lossless codec saves space, and a lossy codec saves much more.
| Symptom | Likely cause | Fix |
|---|---|---|
| File will not open | Unsupported AIFF-C compression code | Re-export as plain integer PCM |
| Recording stops at 4 GB | 32-bit size field reached | Split the take or use a 64-bit container |
| Tags disappear after conversion | Target format stores metadata differently | Re-tag or use a converter that maps tags |
| Pitch or speed is wrong | Sample rate parsed incorrectly | Use a mature library or audio tool |
Another frequent mistake is assuming that converting an MP3 to AIFF restores lost quality. The resulting file is larger, but it still contains only the detail the lossy encoder kept.
A plain-language summary
An AIFF file is like a full-size photograph of a sound rather than a compressed snapshot. Every tiny measurement of the audio is stored exactly as it was recorded, so nothing is lost and the sound can be edited again and again without damage.
The cost is size: an AIFF file is several times larger than an MP3. It is the format to use while working on audio or keeping a perfect copy, not usually the one sent to a phone for everyday listening.
An example from practice
A sound designer builds a sampled piano instrument for a music production company. Each note is recorded at 48 kHz and 24-bit and saved as an AIFF file, because the format’s instrument chunk can store the root note and sustain loop points that the sampler software reads automatically.
The finished library contains several hundred files and is delivered to musicians on both macOS and Windows. Since every major sampler and DAW reads plain big-endian AIFF, the instrument loads correctly everywhere. For the online preview, the same recordings are converted to a compressed format, while the AIFF masters stay in the archive as the untouched source for future updates.