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

Audio format arguments generate more heat than almost any topic in consumer technology. The underlying facts are fairly simple, and knowing them saves both storage and money.

Lossy and lossless

Lossy formats discard audio data permanently, targeting the parts psychoacoustic models predict you are least likely to notice. The file gets much smaller. The discarded data never comes back.

Lossless formats compress without discarding anything, the way a ZIP file does. Decompressed, they are bit-for-bit identical to the source. Roughly half to two-thirds the size of uncompressed audio.

Uncompressed formats store the raw samples with no compression at all.

The formats

MP3 — lossy

Universally supported, plays on anything made in the last twenty-five years. Modern encoders at 320 kbps or high-quality VBR are transparent to most listeners on most equipment.

Use it for: maximum compatibility, or a library that has to fit in limited space.

AAC — lossy

Technically better than MP3 at the same bitrate — noticeably so below 192 kbps. It is what Apple Music and YouTube use, and what iTunes purchases are encoded in. Support is near-universal on modern devices.

Use it for: the default lossy choice on Apple devices.

FLAC — lossless

The standard for lossless. Free, open, excellent tag support including embedded artwork. Around 50–60% the size of the equivalent WAV.

Historically awkward on iOS because Apple favoured ALAC, but third-party players handle it fine — including Offline Music Player.

Use it for: archiving, and for music you want at full quality.

ALAC — lossless

Apple's lossless format. Functionally equivalent to FLAC in quality and similar in size; better native support across Apple software. FLAC has broader support everywhere else.

WAV — uncompressed

Raw audio. Large — around 10 MB per minute for CD quality. No quality advantage over FLAC, which is the same data compressed, and its tag support is poor.

Use it for: audio production, where you are editing repeatedly. Not for a phone library, where it wastes storage for nothing.

Bitrates worth using

• Below 128 kbps — audible artefacts on most material. Avoid for music.
• 128–192 kbps — acceptable for spoken word, adequate for casual listening.
• 256 kbps AAC — what Apple Music streams. Transparent for the large majority of listeners.
• 320 kbps MP3 — the practical ceiling for MP3.
• Lossless — no artefacts by definition. Worth it for archiving; audibly identical to good lossy encoding in most real listening conditions.

Can you actually hear the difference?

Honestly: usually not, in normal conditions. Properly conducted blind tests consistently show most listeners cannot reliably distinguish 256 kbps AAC from lossless on typical equipment.

It becomes more likely with:

• Good headphones in a quiet room — not earbuds on a train.
• Material with lots of high-frequency detail — cymbals, strings, applause.
• Deliberate A/B comparison rather than casual listening.

The honest position: keep lossless for archiving because storage is cheap and it costs you nothing to have the original intact. Do not expect a revelation when you play it.

A practical approach

1. Archive in FLAC on a computer or drive. This is your master copy, and you can convert to anything from it.
2. Put lossless on the phone if storage allows.
3. Convert to 256 kbps AAC if it does not. About a fifth of the size, and you still have the FLAC.
4. Never convert lossy to lossy — each pass compounds the damage.

Whatever you choose, tag the files properly before importing. Format determines quality; tags determine whether you can find anything. How to organise a local music library covers that.