MP3 vs AAC vs FLAC vs OGG: Audio Formats Compared

All audio formats trade quality against file size against compatibility. Here is the short, practical version.

MP3 — plays on everything

The oldest and least efficient of the lossy formats, but every device made in the last 25 years plays it. Choose MP3 when compatibility is the priority: car stereos, cheap players, sharing with unknown recipients. Convert anything with WAV to MP3 or M4A to MP3.

AAC / M4A — better quality per megabyte

The successor to MP3, used by YouTube, Apple Music and most streaming services. At the same bitrate it simply sounds better than MP3. Use it when the target device is modern (any smartphone).

FLAC — lossless archive

Compresses the original audio to ~50-60% without losing a single bit. The format for music collections, masters and anything you might re-encode later. Files are 5-10x larger than MP3. FLAC to MP3 is the classic "shrink my library for the phone" conversion.

OGG Vorbis and Opus — open and efficient

Opus is technically the best lossy codec today, especially for voice and low bitrates: it is what Discord, WhatsApp and Telegram use for calls. The only weakness is patchy support in older hardware. Great for podcasts and voice notes.

Rule of thumb

  • Maximum compatibility → MP3
  • Modern devices, streaming → AAC
  • Archiving, audiophile needs → FLAC
  • Voice, calls, low bandwidth → Opus
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Bitrate cheat sheet

For the lossy formats above, bitrate is the main quality dial: 320 kbps is effectively transparent for MP3 and AAC on normal listening equipment, 192 kbps is a solid middle ground for casual listening, and 128 kbps is acceptable for speech but shows audible compression on music. Opus reaches similar perceived quality at noticeably lower bitrates than MP3 — 96-128 kbps Opus competes with 192 kbps MP3 — which is why it works so well for voice calls over limited bandwidth.

Lossless vs lossy: the bigger picture

FLAC belongs to a small family of lossless formats alongside WAV and ALAC — all reproduce the source exactly, just with different amounts of compression. MP3, AAC, OGG and Opus are lossy: each discards some data permanently, and repeated re-encoding between lossy formats compounds that loss. A safe habit is to keep one lossless master file and generate lossy copies from it for everyday listening, rather than converting lossy-to-lossy repeatedly. Re-encoding a file that is already lossy — MP3 to AAC, for instance — stacks the original loss on top of a new one, so the result is never better than either source alone.