About M4A and WAV

M4A is AAC audio in an MP4 container — the default format of the Apple ecosystem and most streaming services. AAC compresses more efficiently than MP3, so the same bitrate sounds a little better.

WAV is uncompressed PCM audio — the raw samples with a small header. It's the standard interchange format for recording, sampling, and production work, at the cost of roughly 10 MB per minute of stereo.

Converting M4A to WAV produces a lossless file, though detail already discarded by M4A's compression can't be recovered — the new file is a faithful copy of the M4A, not of the original recording.

How the conversion works

This tool runs FFmpeg — the same engine behind most media software — compiled to WebAssembly, entirely in your browser. Your file is read locally, converted locally, and saved straight from memory; nothing is ever uploaded, which also means no queues and no server-side file size limits.

The converter itself is a one-time ~31 MB download on your first conversion, cached by the browser afterwards. Once it's loaded, everything works offline.