What is lossless audio?
Lossless audio keeps every bit of the original recording. Here's how it differs from MP3 and AAC, which formats and streaming services use it, what it costs in file size, and why it matters when a client is judging your mix.
Updated October 2026 · Mixrounds guides
Lossless vs lossy
Every digital recording is a stream of samples. A lossless file stores all of them, either as they are (uncompressed) or packed more efficiently (lossless compression). Decode it and you get the original back, bit for bit.
A lossy codec analyses the audio, models what the ear is likely to miss, such as quiet detail masked by louder sounds or the very top of the frequency range, and throws that away. The file shrinks a lot. The removed data is gone for good, so converting an MP3 back to WAV makes it bigger without making it any better.
Lossless and lossy formats
| Format | Type | Notes |
|---|---|---|
| WAV | Lossless, uncompressed | The studio default. Universally supported; large files. |
| AIFF | Lossless, uncompressed | Apple's equivalent of WAV. Same quality, same size. |
| FLAC | Lossless, compressed | Open format. Typically about half to two-thirds the size of the WAV. |
| ALAC | Lossless, compressed | Apple Lossless. Used by Apple Music and iTunes. |
| MP3 | Lossy | Everywhere, small, fine for casual listening. Not for judging a mix. |
| AAC | Lossy | More efficient than MP3 at the same bitrate. Used by many streaming services. |
| Ogg Vorbis, Opus | Lossy | Open lossy codecs, common in web and app playback. |
CD quality, hi-res and bit depth
Two numbers describe a lossless file. Sample rate is how many samples per second (44.1 kHz, 48 kHz, 96 kHz). Bit depth is how precisely each sample is stored (16-bit, 24-bit), which sets the dynamic range.
- CD quality: 16-bit / 44.1 kHz. Still the baseline for most lossless streaming.
- Hi-res: 24-bit at 48 kHz or above, such as 24-bit / 96 kHz. Common for studio sessions and some streaming tiers.
- 32-bit float: a working format inside DAWs, with huge headroom. Usually converted to 24-bit for delivery.
A higher number is only meaningful if the source has it. Converting a 16-bit file to 24-bit, or upsampling 44.1 kHz to 96 kHz, adds size, not detail.
How big are lossless files?
| Stereo audio | Approx. size per minute |
|---|---|
| WAV 16-bit / 44.1 kHz | 10.6 MB |
| WAV 24-bit / 48 kHz | 17.3 MB |
| WAV 24-bit / 96 kHz | 34.6 MB |
| FLAC 24-bit / 48 kHz | roughly 9–12 MB (varies with the music) |
| MP3 320 kbps | 2.4 MB |
That's why a four-minute mix at 24-bit / 48 kHz is about 70 MB, already well past the roughly 20–25 MB attachment limit of most email providers.
Which streaming services offer lossless?
At the time of writing, these services offer lossless playback on at least some plans:
- Apple Music: lossless ALAC, including hi-res, at no extra cost.
- Amazon Music Unlimited: lossless HD and hi-res Ultra HD.
- Tidal: lossless FLAC, including hi-res.
- Qobuz: lossless FLAC up to hi-res.
- Spotify: lossless for Premium subscribers in supported markets, rolled out from late 2025.
Plans and limits change, so check each service's current settings. Even with a lossless plan, playback may drop to a lossy stream on a weak connection or over Bluetooth.
Can you hear the difference?
For casual listening on typical gear, a high-bitrate lossy file (256–320 kbps) is very hard to tell apart from lossless in a blind test. That changes when someone is listening critically to judge a mix. Lossy encoding can soften transients, narrow or smear the stereo image, and add swirly artifacts on cymbals, reverbs and wide synths: exactly the details a client comments on.
Encoding can also raise peaks. Mastering engineers often leave around 1 dB of true-peak headroom, for example a ceiling of -1 dBTP, so that streaming services' lossy encodes don't clip.
What it means for mix and master engineers
- Review on lossless. Send clients the WAV or FLAC, not an MP3 bounce, so their notes are about your mix and not the codec.
- Deliver at the session's resolution. Usually 24-bit WAV at the session sample rate, plus whatever the distributor or label asks for.
- Don't upsample to look hi-res. Deliver what the session actually is.
- Check the encode. If loudness or clarity matters on streaming, listen to a lossy encode of your master before you sign off.
For delivering multitrack parts, see what stems are and how to deliver them.
Lossless review in Mixrounds
Mixrounds accepts WAV, FLAC and MP3 uploads of up to 500 MB per file and doesn't transcode them: your client streams the exact file you uploaded, in the browser, from the same portal link where they leave timestamped comments on the waveform. On your side, each version shows its format, sample rate and bit depth, so you can confirm you sent the right bounce.
Frequently asked questions
Is FLAC lossless?
Yes. FLAC compresses audio the way a zip file compresses a document: the file is smaller, but it decodes back to exactly the same samples as the original WAV. Nothing is thrown away.
Is WAV better quality than FLAC?
No. A WAV and a FLAC made from the same source decode to identical audio. WAV is uncompressed and larger; FLAC is compressed and smaller. Choose WAV when a tool or client expects it, FLAC when file size matters.
Is a 320 kbps MP3 lossless?
No. MP3 is lossy at every bitrate. A 320 kbps MP3 sounds very close to the original for most listening, but the encoder has permanently removed information, and you can't get it back by converting the MP3 to WAV.
What is hi-res audio?
Usually lossless audio above CD quality: 24-bit at 48 kHz or higher, such as 24-bit/96 kHz. CD quality is 16-bit at 44.1 kHz. Hi-res files are larger, and whether the extra resolution is audible depends heavily on the recording, the playback chain and the listener.
Can Bluetooth headphones play lossless audio?
Mostly not. Common Bluetooth codecs such as SBC and AAC are lossy, so a lossless stream is re-encoded on its way to the headphones. A few newer devices support lossless Bluetooth codecs, but for critical listening a wired connection is still the reliable option.
Should I send clients lossless files to review a mix?
Yes. Lossy encoding can smear transients, narrow the stereo image and add artifacts, so a client reviewing an MP3 may comment on something that isn't in your mix. Send the WAV or FLAC you'd actually deliver, and keep MP3s for casual previews.