MP3 vs AAC vs FLAC vs WAV: an audio format primer

Audio formats split into two camps: lossy (data is discarded to make files smaller) and lossless (every audio sample is preserved exactly). MP3 and AAC are lossy. FLAC and WAV are lossless. Within each camp there are real differences, and within the lossy/lossless divide there are clear use cases for each format. Picking the right one depends entirely on what you're doing with the file.

MP3 (1993)

MP3 is the format that defined consumer digital audio. It's lossy, it's extremely compatible (every device, every player, every car stereo plays MP3), and it produces files about 10× smaller than the equivalent uncompressed audio at typical bitrates. The patents that protected MP3 expired in 2017, so it's now fully royalty-free.

Quality at MP3 bitrates: 320 kbps is the highest MP3 produces and is essentially transparent for most listeners. 192 kbps is the sweet spot for music — small enough to carry around in large libraries, high enough that quality issues don't bother typical listeners. 128 kbps is fine for voice content (podcasts, lectures) but starts to show artifacts on music. Below 128 kbps, the artifacts become obvious — not recommended for music.

Use MP3 when: you need maximum compatibility (every device plays MP3), you're distributing podcasts or voice content, you're producing audio for embed in web pages with broad browser support, or you don't want to worry about codec compatibility on the receiving end. MP3 is the safe default.

AAC (1997, M4A container 1999)

AAC (Advanced Audio Coding) is the lossy format that succeeded MP3 in most ways. It compresses better at the same bitrate (a 128 kbps AAC sounds noticeably better than a 128 kbps MP3), supports more channels for surround audio, and is the default format for Apple's ecosystem (iTunes, Apple Music, the iPhone Camera app's video audio track).

AAC files most commonly carry the .m4a extension (when in an MP4 container) or .aac (when in a raw AAC stream). They sound slightly better than MP3 at every bitrate and produce slightly smaller files at equivalent quality.

Use AAC when: you're targeting Apple devices, you want slightly better quality than MP3 at the same file size, your destination platform supports AAC (most modern platforms do), or you're producing video soundtracks (where AAC is the standard audio codec for MP4 files). The main case for MP3 over AAC is universal compatibility — if you don't need that, AAC is a strictly better technical choice.

FLAC (2001)

FLAC (Free Lossless Audio Codec) compresses audio losslessly — the file you decompress is bit-identical to the source PCM audio. Compression ratios are typically 40-60% of the equivalent uncompressed WAV, depending on the music. FLAC has no quality loss whatsoever; it's purely a more efficient way to store the same data.

Use FLAC when: you're archiving music in a quality-preserving format, you're a serious music listener with high-end audio gear (where the difference between FLAC and 320 kbps MP3 is occasionally audible), you're a music producer or audio engineer working with masters, or you're distributing audio that may be re-encoded downstream (lossy transcoding from FLAC produces better results than from MP3 because FLAC has no compression artifacts to amplify).

Don't use FLAC for casual streaming or sharing — the file sizes are 4-6× larger than equivalent MP3 with no audible benefit on typical playback hardware. FLAC is for archival and audiophile use, not everyday distribution.

WAV (1991)

WAV is the granddaddy of digital audio — an uncompressed PCM format from Microsoft, used for nearly everything in professional audio production. WAV files are huge (about 10 MB per minute of stereo CD-quality audio), but they're also dead simple, universally readable, and have no compression artifacts because they have no compression.

Use WAV when: you're producing audio (recording, mixing, mastering — DAWs work natively in WAV), you're feeding audio into a tool that requires uncompressed input, you're archiving the highest possible quality master that may eventually be re-encoded multiple ways, or you're working with audio samples for music production.

Don't use WAV for distribution or storage of large libraries — the file sizes make it impractical. WAV is for production; encode to FLAC for archival or to MP3/AAC for distribution.

Bitrate guide for lossy formats

• 64 kbps: Voice-only (podcasts, lectures) at the lower end of acceptable quality. Audible artifacts on music.
• 128 kbps: Voice content sounds great. Music has subtle artifacts but is acceptable. The minimum for music distribution.
• 192 kbps: The sweet spot for music. Most listeners cannot reliably distinguish from lossless on typical playback gear. Strongly recommended for music libraries.
• 256 kbps: High-quality music. Apple Music's default streaming bitrate (in AAC). Audiophiles may still notice differences from lossless on excellent gear.
• 320 kbps: The maximum for MP3 and AAC. Essentially transparent to all listeners. Worth using for music you'll listen to repeatedly on good gear.

The transcoding trap

Lossy audio compounds when re-encoded. Convert MP3 to MP3 (at any settings) and you've gone through two lossy passes — the second one degrades quality beyond what either pass alone would. Converting MP3 to FLAC does not restore quality; it just stores the already-degraded MP3 audio in a lossless wrapper.

The right workflow: keep your master audio in WAV or FLAC, encode to MP3 or AAC once for distribution, never re-encode lossy. If you need to make changes, edit the lossless master and re-encode the distribution copy from scratch.

Convert between audio formats

MP3 to WAV, M4A to MP3, FLAC to MP3, WAV to FLAC, and any other audio pair — free, lossless conversion between lossless formats, and quality-preserving encoding for lossy targets.