Reduce WAV File Size on Mac Without Losing a Bit

Use a lossless format. FLAC and Apple Lossless (ALAC) both pack the same samples into fewer bytes, like a zip file for audio. Nothing is thrown away. Both are built into macOS:

afconvert -f flac -d flac in.wav out.flac
afconvert -f m4af -d alac in.wav out.m4a

Do not take that on trust. We checked by decoding each result back to PCM and comparing a hash of the samples. The WAV, the FLAC from afconvert, the FLAC from ffmpeg and the ALAC file all produced the identical hash, f80be164f23035e9bfcb2f543a71b571. That is a bit-for-bit match.

Read those percentages carefully. Our clip is a tone plus noise, which is unusual audio. A pure sine wave shrank from 10,584,078 to 744,873 bytes (7%) as FLAC, because it is very predictable. Real music and speech land somewhere in between and depend on the recording, so we are not quoting a typical ratio. Run it on one of your own files and look.

The sizes are within about 1% of each other. Choose by where the file will play. FLAC is the more widely supported format outside Apple software, and ALAC (an M4A file) is the one Apple’s own apps expect, so check your player first. Use FLAC for archives and for sharing with non-Apple users, ALAC for a Music library. For deeper background, see the best audio converter for Mac.

Neither works in places that demand WAV or MP3, such as many hardware samplers, some podcast hosts and older car stereos. In that case you are choosing between a big file and a lossy one.

Anything below lossless throws information away. These are the common shortcuts and what we measured on the same 10,584,078-byte clip:

Mono and 22 kHz each halve a WAV and nothing else. MP3 at 320 kbps beat FLAC on size here, but it is lossy and cannot be turned back into the original. The WAV to MP3 trade-offs are covered in converting WAV to MP3 on Mac, and the bitrate choice in audio bitrate explained.

WAV stores raw samples. The size is sample rate times bit depth times channels times seconds. CD quality (44,100 samples, 16 bits, two channels) is 176,400 bytes per second, which is 10,584,000 bytes a minute, close to our measured 10,584,078 with its header. A one-hour session is about 635 MB. Recording at 24-bit and 96 kHz multiplies that by roughly 3.3.

That explains the fixes. Lossless packing removes redundancy. Lower sample rate, bit depth or channel count removes information. MP3 and AAC remove what the ear is least likely to notice.

If the audio is a finished voice recording for email or a podcast feed, lossless is overkill. Speech at 64 kbps mono is a tiny fraction of a WAV and sounds fine. See how to compress an audio file on Mac. Keep the lossless copy as your master and send the lossy one.

For a handful of WAVs, afconvert is the better tool: free, installed, and the hash check above proves it. A shell loop does a folder in one line:

for f in *.wav; do afconvert -f flac -d flac "$f" "${f%.wav}.flac"; done

Smol earns $29 (once, one Mac) when the folder is mixed and you want it done without Terminal: drop in WAVs, M4As and MP3s together, convert to FLAC or compress to MP3, AAC, Opus and others with a bitrate from 16 to 512 kbps, from a Finder right-click, and nothing is uploaded. We checked losslessness only on afconvert and ffmpeg output, not on Smol’s, so run the same hash test if you need proof. See pricing or batch converting audio on a Mac.