Convert MP3 to FLAC
A lossless FLAC copy of an MP3 for players and libraries that want FLAC, made on your own device.
- Nothing is uploaded
- Works offline after first use
- Open source
- No watermark · limit is your device’s memory; phones hold less
Converts MP3 files to FLAC in your browser, writing 16-bit lossless audio at the MP3’s own sample rate. It is free, and your music is not uploaded: each file is decoded and encoded in this tab. FLAC stores the MP3’s sound exactly as it decodes, so the file gets bigger without getting better. After your first run the page works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
Converting an MP3 to FLAC does not bring back anything the MP3 threw away. MP3 is lossy: when the file was made, detail the encoder judged inaudible was removed for good. FLAC is lossless, so it stores the decoded MP3 exactly, which is the same sound in a bigger file. There are still sound reasons to do it: a player or car stereo that only lists FLAC, a library kept in one format, or a copy you will edit and save again without another round of MP3 loss.
The size change is easy to work out. A 4-minute MP3 at 192 kbps is 5.8 MB (192,000 bits a second × 240 seconds ÷ 8). As 16-bit stereo audio at 44.1 kHz it carries 1,411 kbps, which is 42 MB as a WAV, and FLAC typically packs music to 40 to 60 percent of that. Expect the FLAC to be roughly 17 to 25 MB, three to four times the MP3.
The FLAC is 16-bit and is written at the MP3’s own sample rate, which the result line shows, for example 44.1 kHz. The file holds the audio only: the title, artist and cover art of the MP3 are not copied across.
Going the other way, FLAC to MP3, is the direction that saves space.
How it works
- Drop one or more MP3 files, or tap to pick them.
- FLAC is already chosen. Pick Mono only for a voice recording.
- Convert. One file downloads straight away; several come as a zip.
In your browser, not on a server
Your browser decodes the sound with the decoders it uses to play media on any website. The new file is written in your tab: MP3 by LAME compiled to WebAssembly, WAV by a few lines of code, FLAC by a small lossless encoder in this site’s code (fixed predictors and Rice coding, as the FLAC format describes), and M4A or OGG by the browser’s own AAC and Opus encoders (WebCodecs), packed by Mediabunny (MPL-2.0). WAV and FLAC keep the original sample rate.
Compared with upload-based tools: Online audio converters upload every file, queue it, cap free use at a few files or a few hundred megabytes, and keep the upload for hours. Recordings of meetings, unreleased songs and voice memos are private. Here the files never leave your device and a whole folder converts at once.
Verify it yourself. Give the page a short while after your first run to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Does converting MP3 to FLAC improve the sound?
No. The MP3 has already lost detail, and no converter can put it back. The FLAC sounds the same as the MP3 and takes much more space. The gain is the format itself: players that want FLAC, and no further loss if you save the file again.
Why is the FLAC so much bigger than the MP3?
The MP3 was packed at a bitrate such as 192 kbps by throwing detail away. FLAC keeps every decoded sample, 1,411 kbps of 16-bit stereo before its own lossless packing, so it is several times larger whatever the quality of the source.
Can I make a 24-bit FLAC?
No. This page writes 16-bit FLAC. An MP3 holds no 24-bit detail, so a 24-bit file would be 16-bit sound in a larger box.
Are the song title, artist and album art kept?
No. The FLAC contains the sound only. Add the tags again in a tag editor or your music app, and keep the MP3 as well if you want its tags and cover.
Is it worth converting my whole MP3 collection?
Rarely. If you still have the CDs or lossless downloads, convert from those. A FLAC made from an MP3 takes three to four times the space and sounds identical to the MP3 it came from.
Are my songs uploaded?
No. Each MP3 is decoded and the FLAC is written in this tab, then saved to your disk. Nothing is uploaded, which suits a private collection or unreleased demos.
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Guides
- How to convert WAV to MP3WAV files are large; MP3 is the smaller, more compatible format most people actually need. Here is how to convert between them.
- A free Convertio alternative with no file size capConvertio's free plan caps both file size and how many conversions you get per day. Here is an alternative with no such ceiling.
- How to merge audio filesJoining voice notes, podcast segments or songs end to end is simple once you know the right tool. Here is the desktop way and a private browser way.
- How to reduce MP3 sizeAn MP3 gets smaller when you lower its bitrate, make it mono, shorten it, or switch format. Here is what each saves, with measured results.
- A free CloudConvert alternative for everyday filesCloudConvert measures its free tier in credits tied to conversion time, not files, which makes it hard to predict when you will hit the limit. Here is an alternative with nothing to meter.