Music Tech3 min read

Audio File Formats Explained: WAV, MP3, FLAC, AAC

Which format to use when — lossless versus lossy, bitrates that matter, what streaming platforms want, and the formats to avoid mid-project.

Format choice matters at two points: while you work (always lossless) and when you deliver (depends on where).

Lossless vs lossy

Lossless formats store every sample exactly. WAV and AIFF store them uncompressed; FLAC and ALAC compress them the way a ZIP file does — smaller, with nothing lost.

Lossy formats — MP3, AAC, Opus, Ogg Vorbis — permanently discard audio information using psychoacoustic models that predict what you won't notice. The savings are enormous (roughly 10:1) and the loss is genuinely subtle at high bitrates. But it is permanent.

The formats

FormatTypeUse for
WAVLossless, uncompressedWorking files, mastering, delivery to distributors
AIFFLossless, uncompressedSame as WAV; more common in Apple workflows
FLACLossless, compressedArchiving, distribution to audiophiles, ~50% smaller than WAV
ALACLossless, compressedSame as FLAC, Apple ecosystem
MP3LossyUniversal compatibility, references, demos
AACLossyBetter than MP3 at the same bitrate; Apple and YouTube default
OpusLossyBest quality at low bitrates; streaming and voice

Bitrates that matter

For MP3: 320kbps is transparent for almost all listeners. 192kbps is fine for references. 128kbps is audibly degraded on cymbals and reverb.

For AAC: quality at a given bitrate is better than MP3, so 256kbps AAC roughly matches 320kbps MP3.

The rules that actually matter

1. Never work from lossy files. Importing an MP3 and processing it compounds artifacts. If you separate stems from an MP3, the model is working from already-damaged audio and the stems will be worse.

2. Never master to lossy. Master to 24-bit WAV. Let the distributor or platform encode.

3. Avoid re-encoding. Every lossy encode discards more. MP3 → edit → MP3 is measurably worse than the original.

4. Deliver lossless to distributors. They re-encode for each platform. Give them the best source.

5. Keep your masters. Archive a 24-bit WAV of every finished track. Platforms and formats change; your master shouldn't have to be recreated.

Sample rate and bit depth in one line

Deliver at the sample rate you worked at (44.1kHz or 48kHz is fine — higher is rarely audible) and at 24-bit for masters, 16-bit only for final CD-format delivery.

Related reading: sample rate and bit depth, audio codecs for musicians, and how to export for streaming.

Frequently asked questions

What audio format should I use for mastering?

WAV or AIFF at 24-bit and the project's sample rate. Both are uncompressed and lossless, so no quality is discarded. Never master from or deliver an MP3.

What is the difference between lossless and lossy audio?

Lossless formats like WAV and FLAC preserve every sample of the original. Lossy formats like MP3 and AAC permanently discard audio information judged to be perceptually less important, in exchange for much smaller files.

What format do streaming platforms want?

Almost all want lossless — WAV or FLAC at 16 or 24-bit. They re-encode to their own lossy formats for delivery, so uploading an MP3 means your audio gets compressed twice, which is audible.

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