You’ve just spent £300 on a pair of wireless headphones, paired them up, hit play on Spotify — and you’re wondering why they don’t sound all that different from your old £30 earbuds. The culprit might not be the headphones at all. It might be the file format your music is playing in.
Audio file formats are one of those things most people never think about until they start caring about sound quality. And then suddenly you’re staring at acronyms like FLAC, AAC, ALAC, and OGG wondering what on earth any of it means. The good news? Once you understand the basics, the whole thing clicks into place — and you’ll know exactly which format to use for every situation.
This guide breaks down the most common audio file formats explained in plain English, covering what each one does well, where it falls short, and which ones actually matter for your listening setup.
What Makes Audio Formats Different?
Before getting into specific formats, it helps to understand the two big categories: lossy and lossless.
- Lossy formats (MP3, AAC, OGG) throw away parts of the audio data to make files smaller. The clever bit is they’re designed to discard sounds your ears are less likely to notice — very quiet frequencies masked by louder ones, ultra-high frequencies most adults can’t hear. The trade-off is obvious: smaller files, but you’re not getting the full recording.
- Lossless formats (FLAC, ALAC, WAV) keep everything. Every single bit of audio data from the original recording stays intact. Files are bigger — sometimes five to ten times larger — but what you hear is exactly what was recorded.
There’s a third category worth mentioning: uncompressed formats like WAV and AIFF. These are lossless by definition (nothing’s been removed), but they also don’t compress the data at all, so they’re completely massive. A three-minute song in WAV takes up around 30-50MB. The same track in FLAC might be 15-25MB, and in MP3 about 3-5MB.
The real question isn’t “which format is best?” — it’s “which format is best for how you actually listen to music?”
MP3: The One Everyone Knows
MP3 (MPEG-1 Audio Layer III) has been around since the early 1990s and basically invented digital music as we know it. It’s the format that made Napster possible, filled your first iPod, and is still the most widely supported audio format on the planet.
How it works
MP3 uses psychoacoustic modelling — a fancy way of saying it analyses what your brain actually perceives and strips out the rest. The amount of data kept is controlled by the bitrate, measured in kbps (kilobits per second).
- 128 kbps — the old “standard” quality. Fine for talk radio or background listening, but you’ll notice the difference on decent headphones. Cymbals get splashy, vocals lose detail.
- 192 kbps — a noticeable step up. Acceptable for casual listening.
- 256 kbps — where most people stop being able to tell the difference from the original in blind tests.
- 320 kbps — the maximum for MP3 and the sweet spot. At this bitrate, even on a good pair of over-ear headphones, most listeners genuinely cannot distinguish MP3 from lossless.
The verdict on MP3
MP3 at 320 kbps is perfectly good for the vast majority of listeners. If you’re playing music through Bluetooth speakers at a barbecue or listening on the train with earbuds, you won’t hear what’s missing. Where MP3 falls short is archiving — once you’ve converted a CD to MP3, you can’t get that data back. Always keep a lossless copy of music you own.
AAC: MP3’s Better-Sounding Successor
AAC (Advanced Audio Coding) was designed to be everything MP3 is, but better. It’s the default format for Apple Music, iTunes purchases, YouTube audio, and most streaming services’ standard tiers.
At the same bitrate, AAC consistently sounds better than MP3. A 256 kbps AAC file (which is what Apple Music downloads at) is roughly equivalent to a 320 kbps MP3. It handles complex passages better — think orchestral swells, dense rock mixes, or anything with lots happening at once.
The only downside is compatibility. While AAC plays on virtually every modern device (iPhones, Android phones, smart speakers, car stereos), some older hardware and niche devices might not support it. In practice though, unless you’re using equipment from 2008, AAC is a safe bet.
If you’re choosing between MP3 and AAC for your music library and your devices support both, go with AAC every time.
OGG Vorbis: The Open-Source Option
OGG Vorbis is Spotify’s format of choice, and there’s a reason for that — it’s royalty-free and sounds excellent at lower bitrates. Spotify’s “Very High” quality setting streams at 320 kbps OGG Vorbis, and it sounds superb.
You’ll rarely encounter OGG files in the wild outside of Spotify and some video games. It’s not a format you’d typically choose for your own music library because hardware support is patchier than MP3 or AAC. But if you’re a Spotify listener, you’re already using it — and it’s doing a brilliant job.
FLAC: The Audiophile’s Best Friend
FLAC (Free Lossless Audio Codec) is where things get interesting for anyone who cares about sound quality. It’s lossless compression — meaning the file is smaller than the raw recording, but when you play it back, every single bit is identical to the original.
Think of it like a ZIP file for audio. When you unzip a document, you get exactly what went in. FLAC does the same thing, just optimised specifically for audio data. A typical FLAC file is about 50-60% the size of the equivalent WAV.
Why FLAC matters
- No quality loss whatsoever. What was recorded is what you hear. Period.
- Supports metadata. Album art, track titles, artist info — it’s all embedded in the file, unlike WAV.
- Widely supported. Most modern DAPs (digital audio players), hi-fi streamers, Android phones, and media players handle FLAC natively. Apple devices are the notable exception — more on that in a moment.
- Future-proof. Your FLAC library will sound exactly as good in 20 years as it does today. You can always convert FLAC to any lossy format later without going back to the CD.
Where to get FLAC music
Services like Qobuz, Tidal (with HiFi), Deezer HiFi, and Amazon Music Unlimited all offer lossless streaming. For downloads, Bandcamp is brilliant — most artists offer FLAC as a download option. You can also rip your own CDs to FLAC using free software like Exact Audio Copy (Windows) or XLD (Mac).
Expect FLAC files to run about 15-35MB per track depending on the recording. If you’ve got a 256GB phone with a decent chunk of free storage, carrying a few hundred albums in FLAC is entirely practical.
Can you actually hear the difference?
Here’s the honest answer: it depends on your equipment and your ears. On a pair of £30 earbuds connected to your phone via Bluetooth, you almost clearly won’t hear a difference between 320 kbps MP3 and FLAC. Bluetooth itself compresses the audio again using codecs like SBC, AAC, or aptX — so you’re adding another lossy step regardless.
Where FLAC shines is with wired connections and decent equipment. Plug a pair of quality over-ear headphones into a proper DAC (digital-to-analogue converter) — even an affordable one like the iFi Zen DAC at about £130 from Amazon UK — and the difference becomes apparent on well-mastered recordings. More air around instruments, better separation, subtle details in the decay of piano notes or the room ambience of a live recording.
But be realistic. If 90% of your listening happens on the morning commute through noise-cancelling earbuds, the convenience of a smaller lossy format probably matters more than theoretical quality improvements you can’t perceive in that environment.
WAV: Raw and Uncompressed
WAV (Waveform Audio File Format) is the simplest audio format — just raw, uncompressed PCM audio data in a container. It’s what sits on a CD (well, CDs use raw PCM, but WAV is essentially the same data with a header).
The pros
- Zero processing. No compression, no encoding, no decoding. Just pure audio data.
- Universal compatibility. Literally everything plays WAV files.
- Studio standard. If you’re recording or producing music, WAV is the working format.
The cons
- Enormous files. A CD-quality track (16-bit, 44.1kHz) runs about 10MB per minute. A hi-res recording (24-bit, 96kHz) can hit 35MB per minute.
- Poor metadata support. WAV technically supports some tags, but implementations are inconsistent. Your carefully tagged album info might not show up in every player.
- No advantage over FLAC for listening. Since FLAC is also lossless but roughly half the size and handles metadata properly, there’s no reason to use WAV for a music library.
The bottom line: WAV is for recording studios, not for listening. If someone gives you a WAV file, convert it to FLAC for storage. You lose nothing in the conversion and gain better metadata support plus smaller files.
ALAC: Apple’s Answer to FLAC
ALAC (Apple Lossless Audio Codec) does exactly what FLAC does — lossless compression with bit-perfect playback — but it’s Apple’s proprietary format. If you’re deep in the Apple ecosystem (iPhone, AirPods Max, HomePod, Apple Music), ALAC is what Apple Music uses for its lossless tier.
The quality is identical to FLAC. File sizes are virtually the same. The only real difference is ecosystem support — ALAC works perfectly on Apple devices, while FLAC requires third-party apps on iOS (though Android handles FLAC natively).
If your entire setup is Apple, use ALAC and don’t worry about it. If you use a mix of devices, FLAC is the safer choice since it works everywhere except Apple’s native apps.
AIFF: The Mac Studio Format
AIFF (Audio Interchange File Format) is Apple’s equivalent of WAV — uncompressed, lossless audio. It offers slightly better metadata support than WAV but creates equally massive files. Like WAV, it’s primarily a studio format. Most listeners will never need to think about AIFF.
Which Format Should You Actually Use?
This is where it gets practical. Your choice depends on three things: what you’re listening on, how much storage you have, and how much you care about audio quality.
For everyday streaming
Whatever your streaming service uses is fine. Spotify at “Very High” (320 kbps OGG), Apple Music at “High Quality” (256 kbps AAC), or YouTube Music at 256 kbps AAC — all of these sound excellent for daily listening. If your service offers a lossless tier and you’ve got the data allowance, switch it on and forget about it.
For your own music library
Keep master copies in FLAC (or ALAC if you’re all-Apple). Always. Even if you can’t hear the difference right now, you might upgrade your equipment later, and you can’t un-compress a lossy file. Think of FLAC as your insurance policy.
For copies on your phone where storage is tight, 256 kbps AAC or 320 kbps MP3 will serve you perfectly well.
For hi-fi and critical listening
FLAC, no question. Pair it with a decent DAC and wired headphones or speakers. Services like Qobuz even offer hi-res FLAC (24-bit, up to 192kHz) if you want to go beyond CD quality. Whether hi-res makes an audible difference over standard CD-quality FLAC is hotly debated — the British Sound Recording Association has published papers on both sides — but having the option is nice.
For vinyl rips and archiving
WAV or FLAC at the highest resolution your equipment supports. If you’ve gone to the trouble of setting up a turntable with a phono preamp and recording your vinyl collection digitally, don’t bottleneck it with a lossy format. Record in WAV, archive in FLAC.
Understanding Bitrate, Sample Rate, and Bit Depth
These three numbers pop up constantly in audio discussions, so here’s what they actually mean.
- Bitrate (kbps) — how much data per second the audio uses. Higher bitrate = more data = better quality in lossy formats. Lossless formats have variable bitrates since they adapt to the complexity of the music.
- Sample rate (kHz) — how many times per second the audio is measured. CD quality is 44.1kHz (44,100 samples per second). Hi-res goes up to 96kHz or 192kHz. The human ear tops out at roughly 20kHz, so 44.1kHz captures everything you can physically hear — the extra headroom in hi-res arguably helps with filtering accuracy, but the audible benefit is marginal at best.
- Bit depth (bits) — the precision of each sample. CD uses 16-bit (65,536 possible values per sample). Hi-res uses 24-bit (over 16 million values). Higher bit depth means better dynamic range — the difference between the quietest and loudest sounds in a recording. For playback, 16-bit offers 96dB of dynamic range, which exceeds what most music uses. 24-bit matters more for recording and mixing where the extra headroom prevents clipping.
Quick Format Comparison
- MP3 — lossy, tiny files (~1MB/min at 128kbps, ~2.5MB/min at 320kbps), plays everywhere, good enough for most listening
- AAC — lossy, better quality than MP3 at same bitrate, default for Apple and YouTube, excellent all-rounder
- OGG Vorbis — lossy, open-source, Spotify’s format, great quality but limited hardware support
- FLAC — lossless, compressed (~5MB/min CD quality), wide support except Apple native apps, ideal for archiving and hi-fi
- ALAC — lossless, compressed, Apple’s equivalent of FLAC, same quality and size
- WAV — uncompressed lossless (~10MB/min CD quality), studio standard, poor metadata, no reason to use for listening
- AIFF — uncompressed lossless, Apple’s WAV equivalent, slightly better metadata
Frequently Asked Questions
Can you hear the difference between MP3 and FLAC? It depends on your equipment and listening environment. On budget earbuds or Bluetooth connections, most people cannot tell the difference. With quality wired headphones and a decent DAC, trained listeners can often distinguish between lossy and lossless formats, particularly on well-mastered recordings with complex instrumentation.
What audio format does Spotify use? Spotify uses OGG Vorbis at up to 320 kbps on its premium tier. The free tier streams at lower bitrates. Spotify has announced plans for a lossless HiFi tier but has not yet launched it in the UK as of 2026.
Is FLAC better than WAV? For listening purposes, FLAC is better than WAV. Both are lossless and sound identical, but FLAC files are roughly half the size and support metadata (album art, track info) much more reliably. WAV is primarily used in recording studios where processing overhead needs to be minimal.
What is the best audio format for iPhone? For lossy playback, AAC at 256 kbps is the best choice for iPhone as it's Apple's native format. For lossless, ALAC (Apple Lossless) works natively with Apple Music and iOS. FLAC requires third-party apps like VLC on iPhone.
Does Bluetooth reduce audio quality? Yes. Bluetooth uses its own audio codecs (SBC, AAC, aptX, LDAC) to transmit audio wirelessly, and most of these add lossy compression. Even if you're playing a FLAC file, Bluetooth will re-encode it. The best Bluetooth codecs like LDAC can transmit near-lossless quality, but for true lossless playback, a wired connection is still necessary.