MP3, FLAC, AAC and the Rest: What Each Format Actually Is

You listen every day. Do you know what's in the file?

A friend doing a podcast sent me a file last week, proudly announcing he'd recorded it lossless. I opened it: .wav, 400 MB for one episode. WeChat wouldn't take it, email wouldn't take it. I asked whether the episode was going to a platform or sitting on his hard drive as an archive. Silence.

That's a textbook case. A lot of people never get past one idea: audio formats aren't a quality leaderboard, they're a set of trade-offs. If you want portability, distribution and small files, stop obsessing over lossless. If you want monitoring, mixing and critical listening, stop complaining about size.

So let's go through the usual suspects one at a time. No definitions to memorize — plain language only.

1. MP3: the old workhorse

Nobody needs an introduction. MPEG Audio Layer III is in your phone, on flash drives, and was on every iPod.

The full name is dry — MPEG Audio Layer III, layer three of the Moving Picture Experts Group's audio spec — but you only need one sentence: it invented lossy compression as we know it.

How lossy? A three-minute song is about 30 MB on a CD. MP3 cuts that to three to five, removing 80 to 90 percent of the size. What goes is mostly the frequency detail your ear pays least attention to. At 128 kbps it's "fine" on ordinary earbuds. At 320 kbps it's solid — unless you have genuinely trained ears, you won't find much to complain about.

• Upside: small, absurdly compatible, plays on anything, sends over WeChat instantly
• Downside: the detail is gone, and re-encoding degrades it further, like photocopying a photocopy

So the role is unambiguous: MP3 is a delivery format, not a production format. Sending to someone, uploading to a podcast host, setting a ringtone — MP3 is always the safe call.

2. WAV: fat, but honest

WAV (say "wave") is Microsoft's standard digital audio format for Windows. The approach is charmingly blunt: however the sound looks, store that waveform exactly as it is.

Quality? Maximum. Distortion? Essentially none. The problem? It's enormous.

A song is easily 30 to 50 MB, and a two-hour conversation recording heads into the hundreds of megabytes. That's precisely why my friend couldn't send his file.

When do you use it? For recording, editing and mixing — the working copy. You can't cut MP3 as your source over and over; every pass costs you quality. The professional pipeline is record WAV, edit, mix, then export MP3 for listeners. WAV is for doing the work, not for sending it.

3. WMA: Microsoft's own, now a bit cold

Windows Media Audio was Microsoft's attempt to fight MP3. Technically it wasn't bad — at low bit rates it competes well and files are small.

But it lost the ecosystem. Almost nobody saves new audio as WMA; phones, editors and podcast platforms prefer MP3 and AAC. It's the smart kid nobody picked for the team.

Verdict: if you run into one, treat it as ordinary audio. Don't archive anything new in it — compatibility is a latent problem.

4. FLAC: the audiophile religion, and genuinely lossless

FLAC is Free Lossless Audio Codec. The key word is lossless.

Careful: lossless doesn't mean better than CD. It means the WAV data is compressed and packaged such that unpacking it gives you a file identical to the original, byte for byte. Size drops by roughly 40 percent, and it sounds exactly the same.

It suits two groups:

• Audiophiles: thousands of FLAC files on a NAS, played through a good DAC and headphones — clean highs, solid lows, indistinguishable from the disc
• Post-production people: keeping a master-quality copy so a future remix doesn't start from a degraded source

The practical problem: platforms don't want it, WeChat complains, and phone storage weeps. So for everyday listening, don't fight yourself — archive in FLAC, go out in MP3 or AAC.

Quietly: on a cheap pair of Bluetooth earbuds, you may not hear any difference between FLAC and a 320 kbps MP3. Don't hit me.

5. MIDI: it isn't sound at all

This one is misunderstood most often. MIDI isn't recorded music — it's a digital score.

What's stored isn't a waveform but instructions: which track, which instrument, which key, how long, how hard. So a few minutes of MIDI is a few kilobytes to a few dozen, and it can carry dozens of tracks.

What you hear is a synthesizer performing the score. No vocals, no recorded performance. Its home is arranging, ringtones (old phone ringtones were all MIDI), game soundtracks and composers sketching ideas.

If that's not your world, one line is enough: it's a score for a machine to read.

6. RA: a period piece

RA (RealAudio) is nostalgia for anyone who was online early. Back on dial-up at 56 kbps, listening to a song meant streaming it while it downloaded, and RA did exactly that — the grandfather of streaming, automatically dropping quality to match your bandwidth. It stuttered, but it played.

Today? Essentially nobody. Its only remaining job is reminding us how hard listening to music used to be 😭

7. APE: the other lossless camp, niche but serious

APE is lossless too, courtesy of Monkey's Audio, squeezing a fat WAV into a smaller APE with the quality untouched.

Sounds like FLAC, right? It is, basically. The differences: FLAC is open source and widely supported, APE compresses slightly harder but its software ecosystem is small. FLAC has won; APE has a loyal old guard.

My advice: archive new material straight to FLAC and don't add another format to your life.

8. AAC: MP3's successor, and the quiet king of phones

AAC (Advanced Audio Coding) is lossy, but smarter than MP3. It uses a more modern algorithm — better sounding at the same bit rate, better quality at the same size.

You use it constantly without noticing: Apple Music, YouTube, TikTok, iPhone recordings and ringtones (.m4r is AAC underneath), and live streaming. All AAC.

One line for its position: AAC is the quality floor of the modern internet. Newer than MP3, cheaper than FLAC, and the actual boss of delivery.

9. CDA: the file that pretends to be one

Anyone who's used a CD player has seen .cda files — one icon per track, looking perfectly legitimate.

But CDA isn't audio data. It's just an index pointer to a track on the disc; the actual sound is pressed into the disc's audio track. Copy a CDA to your computer and you get a few dozen kilobytes that won't play, because there was never any sound in it.

Standard CD audio is 44.1 kHz sampling at 16-bit, about 1411 kbps, close enough to lossless — which is why the "you are there" feeling of a CD player had a physical basis.

To get a digital copy, rip the disc to WAV or FLAC with ripping software. Don't just copy the CDA icon — that's the classic beginner crash.

10. MOV: wait, isn't that video?

Correct. MOV is Apple's QuickTime container, and it can hold video, or audio only. Calling it a pure audio format is a stretch, but anyone making vlogs or cutting video touches it daily.

It's popular as a high-quality intermediate because it handles multiple audio tracks and high bit rates without much compression. Windows can play it (with a codec or VLC), and phones generally cope.

For video people: export working clips from CapCut or Final Cut as MOV for quality, then deliver H.264 plus AAC. Don't hand a client a raw MOV — they may not be able to open it.

One table, and a few blunt truths

Format	Lossy / lossless	Size	What it's for
MP3	Lossy	Small	Distribution, phone listening, podcast publishing
WAV	Lossless (uncompressed)	Huge	Recording, editing, masters
WMA	Lossy	Small	Avoid if you can
FLAC	Lossless	Large	Archiving, critical listening, keeping sources
MIDI	Instructions	Tiny	Arranging, ringtones
RA	Lossy	Small	Archaeology only
APE	Lossless	Large	Old-school enthusiasts
AAC	Lossy	Small	Streaming, video audio
CDA	—	Not a file	Disc index, don't copy it
MOV	Container	Depends	Video / high-quality intermediates

If you take one thing away: stop using one format for everything.

Record in WAV, keep FLAC as the master, deliver in MP3 or AAC, and listen on your phone at 320 kbps MP3. Get that sequence straight and you'll never again have a file too big to send, or audio so degraded you can't stand to hear it.

Ready to convert something? Audio Converter handles MP3 and WAV in both directions with the bit rate under your control, and Video Converter pulls the audio out of a clip. Everything runs in your browser: no uploads, no retention. Your privacy is fully protected.

That's it. I'm off to turn his 400 MB WAV into an 80 MB FLAC for storage and an MP3 for the platform. He owes me a bubble tea 🧋

Common questions

What's the real difference between MP3 and FLAC?

MP3 is lossy: it removes frequency detail your ear is least likely to miss, taking a three-minute song down to roughly 3 to 5 MB. FLAC is lossless: unpack it and you get the original back byte for byte, at about 40 percent less than WAV. Use MP3 or AAC for everyday listening and publishing, FLAC to archive the master.

Which format should I record and edit in?

WAV. It's essentially free of distortion and survives repeated editing, which MP3 does not — every pass adds damage. The standard flow is record WAV, edit, mix, then export MP3 or AAC for listeners. Never use an MP3 as your working source.

Why won't a CDA file play after I copy it to my computer?

Because CDA isn't audio. It's an index pointing at a track on the disc, and those files are only a few dozen kilobytes. The sound is physically on the disc's audio track. To keep a digital copy, rip it with ripping software into WAV or FLAC; copying the icon is the classic beginner mistake.

What's the safest format for a podcast platform or for messaging?

MP3 is always the safe delivery choice, and 320 kbps is genuinely solid. If you want better sound at the same size, AAC is the smarter codec, and it's what Apple Music, YouTube, short-video platforms and live streaming use. If the file is too big to upload, compress a version before you send it.

Note: some of the material here was produced with AI assistance.

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