CAF file format (.caf)

What is a CAF file?

In short: A CAF file (.caf) is an audio file in the CAF format. CAF was designed to remove the 4 GB ceiling that WAV and AIFF inherited from their 32-bit headers, so it can hold recordings of essentially unlimited length. It can be converted to MP3, WAV or FLAC for free in a web browser with iHateFiles, without uploading it.

Apple's Core Audio Format, introduced with macOS 10.4 in 2005.

CAF was designed to remove the 4 GB ceiling that WAV and AIFF inherited from their 32-bit headers, so it can hold recordings of essentially unlimited length. It carries almost any codec and detailed per-channel metadata.

What CAF is good at

• No practical size limit
• Holds any codec, compressed or not
• Rich channel and marker metadata

Where CAF falls short

• Apple-centric
• Not supported by browsers
• Less portable than WAV for interchange

When to use CAF

Convert CAF to WAV or M4A to move a recording off a Mac.

How to open a CAF file

macOS, Logic, and VLC.

The thing that usually goes wrong

A CAF can contain compressed audio, so converting one to WAV does not necessarily make it lossless: that depends on what was inside.

Inside a CAF file

Core Audio Format was introduced by Apple in 2005 to get past a limit that had become genuinely awkward: WAV and AIFF both store sizes in 32-bit fields, which caps a file at 4 GB. At 24-bit 96 kHz stereo that is about two hours, and a live recording rig can exceed it in an afternoon.

CAF uses 64-bit offsets, so the practical limit is gone. It also decouples the container from the codec entirely — a CAF can hold uncompressed PCM, ALAC, AAC or IMA ADPCM — and carries markers, regions and channel layout descriptions that a plain WAV cannot.

The reason to convert one is simply reach: outside Apple software almost nothing opens CAF, so a file that is perfectly well-formed is functionally unreadable to whoever you send it to.