FLAC vs MP3

The short answer

FLAC is lossless: it compresses the recording to roughly half the size of WAV and gives back every sample exactly. MP3 is lossy: it is smaller again, by a large margin, and what it discarded is gone. On good equipment and with attention, the difference is audible on some material; on earbuds on a train, it is not.

So this is a question about purpose rather than about quality. FLAC is what to keep a collection in, because anything else can be made from it later without a second loss. MP3 is what to carry, because it fits and because every device made in the last twenty-five years plays one.

The practical arrangement most people end up with is both: FLAC on a computer or a drive as the library, MP3 generated from it for whatever is being carried around. Several music applications will do that conversion automatically when syncing to a device, which is far less work than doing it by hand.

Side by side

Where they actually differ

• They treat the recording differently. One returns every sample exactly as it was given; the other discards sound its encoder judged inaudible and cannot recover it.
• For three minutes of stereo, MP3 produces the smaller file, and the gap is large enough to decide how much fits on a device.
• They are 8 years apart, and most of what separates them is what had been learned in between.

What people get wrong

• Converting from the lossy one to the lossless one does not repair anything. The detail its encoder discarded is not in the file, so what you get is a larger file holding exactly the same damaged image.
• Converting between two lossy formats re-encodes an already-compressed recording, so the result is slightly worse than the input whatever quality you pick. Work from the least-processed copy you have.
• Expect the file to change size substantially in one direction. That is the formats behaving as designed rather than a failed conversion, and it catches people who assume a conversion is roughly size-neutral.

Which to choose

Choose FLAC when

Choose FLAC for archiving and for a library you intend to keep, where the file is the master copy everything else will be made from.

Choose MP3 when

Choose MP3 for a phone, a car, an old player, or anything with limited space — and whenever you are not sure the device reads FLAC.

Converting between them

• FLAC to MP3 converter

Common questions

Can most people hear the difference?

On typical equipment, in typical conditions, no. The difference shows up on good headphones with material that has a lot of quiet detail, and it shows up much faster at low bitrates. At the highest MP3 settings, most listeners are guessing. Keep FLAC for the archive anyway — not because you will hear it today, but because you can make anything from it tomorrow.

Which of FLAC and MP3 is better?

Neither, in general — if one were simply better the other would have disappeared. They are good at different things, and the short answer above says which is which. The useful question is what the file has to do next: be edited, be published, be opened by somebody else, or fit inside a size limit.

Does converting between them lose anything?

It depends on the direction. Converting into a format that stores everything loses nothing but does not recover anything either; converting into one that discards detail loses a little each time. The table above says which of these two does which.

Can I convert back afterwards?

The file will convert back, but whether it comes back unchanged depends on the direction. Between two formats that store everything, a round trip is lossless. Where one of them discards detail, that detail is gone and the return journey cannot invent it.

Can I use both?

On a web page, often yes, and it is usually the right answer: serve the smaller modern format and list an older one as a fallback so each browser takes what it understands. For a file you are handing to a person, pick one — the one they can open.

Which one does my software support?

The side-by-side table above says which browsers read each, which is the part that varies most. Desktop support is harder to state in general and tends to lag browsers by years, so if the file is going to somebody else, the older and more widely read of the two is the safer choice.

Is converting between them free?

Yes, with no account and no limit on how many files you convert. Every converter linked from this page runs in your browser: the file is read from your device, converted by code running on it, and handed back as a download.

Is my file uploaded?

No. There is no conversion server here to upload it to, and no third-party service is involved. You can confirm it yourself: open your browser's developer tools, switch to the Network panel with no filter, and run a conversion — no request carries your file.