If I pick one format for my whole music library, which should it be?

FLAC, if you have enough storage. It's lossless, you can produce whatever format you need later in a single step, and its tagging support is good. If space is tight or you constantly sync the library to a phone, 256 kbps AAC or 320 kbps MP3 is a reasonable compromise. The worst option is keeping five different formats in the same library.

FLAC or MP3 when putting music on my phone?

Think about phone storage and listening conditions. Out and about, on headphones, with background noise, very few people can tell FLAC from 256 kbps AAC. You can carry five times as many songs in the same space. FLAC makes sense for the archive, a lossy format for portable listening.

I have WMA files — what should I do?

Convert them to MP3 or AAC. WMA support has narrowed over the years; modern phones, car systems and a lot of software struggle to read it. Because the conversion goes lossy to lossy, some quality loss is unavoidable — limit it by keeping the target one notch above the source. If a lossless version of the source exists, going from that is always better.

Why isn't Opus more widely used?

Technically it beats MP3 and AAC in most scenarios, especially at low bitrates. What slows its spread is the legacy of compatibility: MP3 has been everywhere for thirty years, from car head units to old MP3 players. Opus is widely used in modern browsers and in apps like WhatsApp and Discord, but hardware support is still limited.

Which Audio Format Should You Choose? MP3, AAC, FLAC, WAV and Opus Compared

There's no single answer to "which audio format is best," because the formats were designed to solve different problems. Archiving, listening on a phone, editing and publishing on the web all have different requirements. This article compares the formats through scenarios.

The formats' basic characteristics

| Format | Type | Typical size (3 min stereo) | Tag support | Compatibility | |---|---|---|---|---| | WAV | Lossless, raw | ~30 MB | Weak | Very high | | FLAC | Lossless, compressed | ~15-20 MB | Very good | Medium-high | | ALAC | Lossless, compressed | ~15-20 MB | Good | Apple ecosystem | | MP3 320 | Lossy | ~7 MB | Good (ID3) | Highest | | MP3 192 | Lossy | ~4.3 MB | Good | Highest | | AAC 256 | Lossy | ~5.5 MB | Very good | Very high | | OGG Vorbis | Lossy | ~4-6 MB | Good | Medium | | Opus 128 | Lossy | ~2.9 MB | Good | Medium (growing) | | WMA | Lossy | ~4-6 MB | Medium | Low |

Scenario 1: Building a music archive

You're digitizing your CD collection or building a long-term library.

Winner: FLAC.

The reasons:

It's lossless. Whatever bitrate you pick today, you may regret it ten years from now. With FLAC there's no such risk — the source data is preserved.

It's future-proof. Whatever format you need later (a new device, a new codec), you can produce it from FLAC in a single step. If you have to start from a lossy archive, every conversion adds more loss.

Tagging support is good. Artist, album, year, genre, cover art and more are stored properly. WAV's tagging support is weak, and that becomes a serious problem in large libraries.

It takes about half the space of WAV. Without giving up losslessness.

Prefer WAV for archiving in only one situation: if the system you use doesn't support FLAC at all. Otherwise FLAC is better in every respect.

Scenario 2: Listening on my phone, out and about

Limited storage, headphone listening, on the move.

Winner: AAC (256 kbps) or MP3 (320 kbps).

You have to be realistic here. Out and about, on headphones, with background noise, very few people can tell FLAC from well-encoded 256 kbps AAC. In exchange you carry five times as many songs in the same storage.

AAC or MP3? If you're in the Apple ecosystem, AAC makes more sense — it's both more efficient and natively supported. In a mixed environment (Android phone, old car head unit, various speakers), MP3 gives you fewer surprises.

Scenario 3: Editing audio

Podcast editing, music production, sound effect work.

Winner: WAV.

During editing the file gets opened, cut, processed and saved many times over. If you work in a lossy format, every save re-encodes and the loss accumulates.

Because WAV is uncompressed:

No re-encoding ever happens.
Editing programs work fastest with this format (opening and seeking are instant).
Every program supports it.

FLAC is also lossless and usable, but every save involves a compress/decompress pass, and that slows things down on large projects.

The workflow: work in WAV, and encode to the target format once when you're done.

Scenario 4: A podcast or audiobook

Speech-heavy content, long duration.

Winner: Opus or low-bitrate AAC/MP3.

Speech requires far less data than music. Bitrates considered low for music are more than enough for speech:

| Format | Sufficient bitrate for speech | |---|---| | Opus | 32-48 kbps | | AAC | 64-96 kbps | | MP3 | 96-128 kbps |

Opus is technically the best in this scenario; it keeps intelligibility even at low bitrates and carries components designed specifically for speech. But its compatibility isn't as broad as MP3's.

If you're distributing a podcast, MP3 is still the safest choice — every podcast app and RSS reader supports it.

Consider using mono. In a single-person speech recording stereo is unnecessary, and mono halves the file size.

Scenario 5: Serving audio on a website

Audio will play on a site or in an app.

Winner: AAC or Opus, with MP3 as fallback.

Every modern browser supports AAC and Opus. Both are more efficient than MP3, so you use less bandwidth at the same quality.

If you also want to support very old browsers, you can offer multiple sources with the <audio> element:

<audio controls>
  <source src="audio.opus" type="audio/ogg">
  <source src="audio.m4a" type="audio/mp4">
  <source src="audio.mp3" type="audio/mpeg">
</audio>

The browser picks the first format it supports.

Scenario 6: An old car head unit or MP3 player

Pre-2010 hardware.

Winner: MP3, no contest.

In this scenario arguing about technical superiority is pointless. Whatever the device reads is what you use. Most old hardware only recognizes MP3; some also read WMA.

Extra things to watch:

There may be a bitrate limit. Some old devices won't play 320 kbps or VBR properly. If you run into trouble, try 192 kbps CBR.
File name and tag encoding. Non-ASCII characters can look garbled on old devices. Simplifying file names can help.
There may be folder depth and file count limits.

Scenario 7: Rescuing my WMA archive

You have an old Windows library.

Winner: converting to MP3 or AAC.

WMA support has narrowed over the years. Modern phones, car systems and a lot of software struggle to read it.

Because the conversion goes lossy to lossy, some loss is unavoidable. To limit it, keep the target bitrate one notch above the source: 128 kbps WMA → 192 kbps MP3.

If a lossless version of the source exists (the original CD, say), going from that is always much better.

Decisions to avoid

Converting lossy to lossless. Turning an MP3 into FLAC doesn't gain quality; it just makes the file five times bigger.

Chained conversion. On a path like MP3 → AAC → OGG → MP3, every step adds loss.

A mixed library. Keeping five different formats in the same collection makes syncing and management harder. Pick one archive format (FLAC) and one distribution format (AAC or MP3).

Unnecessarily high bitrate. Turning a 64 kbps source into 320 kbps gives you a huge file at 64 kbps quality.

Changing the sample rate. Turning 44.1 kHz into 22 kHz cuts the high frequencies and they don't come back. Raising it needlessly gains nothing either.

Decision summary

Archive → FLAC
Portable listening → AAC 256 or MP3 320
Editing → WAV
Podcast/speech → MP3 96-128 (for distribution), Opus (for efficiency)
Web delivery → AAC plus Opus, MP3 as fallback
Old hardware → MP3, 192 kbps CBR if needed
Apple ecosystem → AAC or ALAC

And a rule that applies in every scenario: keep your original source. Having the best possible source on hand for reconverting when your needs change makes every later decision easier.