What is the CAF file format?
A .caf file is an Apple Core Audio Format audio container introduced with macOS 10.4 Tiger and the Core Audio framework in 2006. Apple designed the format to overcome fundamental limitations of the older AIFF and WAV containers: CAF removes the 4 GB file-size cap by using 64-bit chunk sizes, supports any sample rate via a 64-bit IEEE 754 double-precision field, handles any bit depth, and accommodates any number of audio channels natively.
Every .caf file begins with an 8-byte header - the ASCII signature caff, a 16-bit version field (0x0001), and a 16-bit flags field - followed by sequential chunks. Each chunk carries a 4-character type tag, an 8-byte size, and its data payload. Two chunks are required: the Audio Description chunk (desc) specifying the codec and format parameters, and the Audio Data chunk (data) containing the audio samples. Optional chunks cover channel layout, markers, regions, MIDI sync, peak levels, and textual metadata.
CAF supports a wide range of codecs: uncompressed PCM, AAC, Apple Lossless (ALAC), MP3, µ-law, and A-law, among others. It is widely used across Apple's platforms for iOS system sounds, ring tones, voice memos, and professional audio work in GarageBand and Logic Pro. The command-line tool afconvert and FFmpeg both handle .caf conversion. The format has no successor and remains Apple's preferred container for high-fidelity and long-duration audio.
Security & safety
RISK: LOWCAF is an audio container; no known exploit vectors for standard players. Only trust .caf files from known sources when opening with older or unpatched software, as malformed chunk sizes could theoretically cause parser issues.
Format details
in a nutshellPrograms that open CAF files
Windows4 apps
macOS7 apps
afconvert (command line)
Built-in afconvert input.caf output.mp3 -f mp3 -d LEI16@44100 (bundled with macOS) 
Linux3 apps
Technical details
deep spec| File signature | caff (ASCII, bytes 0-3) |
| Format version field | 0x0001 at bytes 4-5 (big-endian; only version defined in specification) |
| Byte order | Big-endian for all header and metadata fields; audio payload byte order depends on codec |
| Container model | Chunk-based: 4-char type tag + 8-byte size + data payload |
| Maximum file size | No 4 GB limit (64-bit chunk size fields) |
| Sample rate field | 64-bit IEEE 754 double in Audio Description chunk (supports any sample rate) |
| Supported codecs | PCM (uncompressed), AAC, Apple Lossless (ALAC), MP3, µ-law, A-law, any CoreAudio-supported codec |
| Required chunks | Audio Description (desc) and Audio Data (data) |
| Channel support | Any number of channels; explicit Channel Layout chunk available |
| Typical size | Few KB (ring tones) to several GB (uncompressed multichannel audio) |
| MIME type | audio/x-caf |
| Associated platforms | macOS, iOS, tvOS, watchOS |
| Integrity check | None (no built-in checksum) |
| Developer | Apple Inc. |
| Released | 2006 (macOS 10.4 Tiger, iOS) |
| Latest version | Core Audio Format Specification 1.0 (2006-03-08; no major revision since) |
| Specification | developer.apple.com |
CAF conversions
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