Convert MP3 to FLAC Online Free
Convert your .mp3 files to .flac format. Free, fast, and processed entirely in your browser — your files never leave your device.
Why MP3 to FLAC will not give you a "lossless" file
We get this conversion request constantly, and almost every time the person asking is hoping FLAC will somehow restore audio quality. It won't — and we'll show you why in plain English. There are three legitimate reasons to convert MP3 to FLAC, but "to make it sound better" is not one of them. Here's the full picture, including when this conversion is actually useful and how to do it cleanly.
When MP3 to FLAC is genuinely useful
- You want to add metadata, album art, or chapter markers that the original MP3 doesn't carry. FLAC has rich metadata support — once your file is FLAC, you can tag it cleanly.
- You're standardizing a music library on a single format. If your library is mostly FLAC and you have a few stray MP3s, converting them to FLAC keeps the directory tidy (just understand they won't sound any better).
- You're feeding a tool or device that only accepts FLAC. Some HiFi DAPs (Astell&Kern, FiiO), audiophile streamers (Roon, BluOS), and edge cases in pro audio require FLAC input.
- You want to freeze the current audio state without re-encoding it. FLAC is lossless, so further conversions or playback won't lose any more quality on top of what MP3 already lost.
When you should NOT convert MP3 to FLAC
- You think it'll restore audio quality. It won't. The data MP3 threw away is gone for good — see the pitfalls section. FLAC preserves whatever you feed it perfectly, but it can't reconstruct what's missing.
- You're trying to save space. FLAC is 5-7× larger than the source MP3 — converting the whole library makes things much worse, not better.
- You're going to play back on your phone, in the car, or over Bluetooth. Almost no consumer playback context distinguishes MP3 from FLAC under normal conditions.
- You're sending the file to someone. FLAC won't be playable on every system out of the box (Apple Music doesn't support FLAC, for instance) and the file is bigger.
How big the FLAC file will be
FLAC is lossless compression, so it expands the audio back to full PCM and then compresses it without throwing data away. The output ends up roughly 5-7× the size of the source MP3 — bigger than a smart compression should be, because it's encoding the full uncompressed signal not the original.
| Duration | MP3 | FLAC | Note |
|---|---|---|---|
| 1 minute | ~0.96 MB (128 kbps MP3) | ~5-6 MB | 5-6× bigger |
| 1 minute | ~2.4 MB (320 kbps MP3) | ~5-6 MB | Higher source MP3 doesn't change FLAC size |
| 10 minutes | ~9.6 MB (128 kbps MP3) | ~50-60 MB | Comparable to a low-bitrate WAV |
| 1 hour | ~57.6 MB (128 kbps MP3) | ~300-360 MB | Half the size of WAV at the same audio |
Source: stereo MP3. Target: 16-bit / 44.1 kHz stereo FLAC at the default compression level (-5). FLAC compression level only affects encode/decode speed, not file size or quality much (~5% range).
Where FLAC plays (and where it does not)
Works with
- VLC, foobar2000, Windows Media Player (with codec), macOS Music app (recently added support)
- HiFi DAPs and audiophile streamers: Astell&Kern, FiiO, HiBy, Roon, BluOS
- Most modern Android phones, smart speakers, and home receivers
- Audacity, Reaper, and most DAWs (FFmpeg-based pipelines all support it)
- Plex, Jellyfin, Emby, and other home media servers
- Browser <audio> element on Chrome, Firefox, Edge (not Safari historically — recent versions added support)
Does not work with
- iTunes/Apple Music ecosystem — Apple uses ALAC (Apple Lossless), not FLAC
- Most car head units (a few high-end ones support it; most do not)
- Most podcast platforms and chat apps don't accept FLAC for upload
- Some Bluetooth devices that decode MP3/AAC in hardware but not FLAC
How to convert MP3 to FLAC
Convert with WaveSieve (browser, free, no upload)
Quickest path. Conversion runs in your browser via FFmpeg.wasm — your file never leaves your device, no account needed.
- Drop your MP3 file onto the upload area at the top of this page. Up to 100 MB per file.
- In the converter, change the output format to FLAC.
- Click "Convert to FLAC". Encoding takes 5-30 seconds depending on file length.
- Click "Download" to save the FLAC. The original MP3 is untouched.
Convert with Audacity (desktop, free, with metadata control)
Use Audacity if you want to add or edit metadata (artist, title, album, year) during the conversion.
- Open Audacity (free at audacityteam.org). Make sure the FFmpeg add-on is installed for MP3 import.
- File → Open → pick your MP3.
- File → Export Audio → choose 'FLAC Files' from the format dropdown.
- In the dialog, set the compression level (any value 0-8 — higher is smaller, all are lossless and identical in audio output). 5 is the default and a good choice.
- Fill in the metadata fields, click Save.
Convert with FFmpeg (command line, batch, scripts)
For batch jobs or pipelines. FFmpeg uses the official libFLAC encoder.
- Install FFmpeg: brew install ffmpeg (macOS), winget install ffmpeg (Windows), or sudo apt install ffmpeg (Linux).
- Open a terminal in the folder with your MP3.
- Single file: ffmpeg -i input.mp3 -c:a flac output.flac
- Specify compression level (0-12, default 5): ffmpeg -i input.mp3 -c:a flac -compression_level 8 output.flac
- Whole folder: for f in *.mp3; do ffmpeg -i "$f" -c:a flac "${f%.mp3}.flac"; done
Things that surprise people
FLAC cannot recover quality the MP3 already lost
This is the single most common misconception we see. MP3 encoding is lossy — it analyzes the audio, throws away frequencies the human ear is unlikely to notice, and saves the result. Converting that to FLAC just wraps the already-degraded audio in a lossless container. The file gets 5-7× bigger, but the audio quality is identical to the source MP3. To get true high quality, you need an uncompressed source (CD, WAV, original master) — not a round-trip through FLAC.
Your MP3 was already 320 kbps? FLAC is still no better
People sometimes think 'high-bitrate MP3 has more to preserve, so FLAC of it must be better.' Same misconception, just bigger numbers. The lossy compression has already happened — every spectral component the encoder discarded is missing. FLAC is just a lossless container around what's left.
Don't convert your whole library in bulk
Converting an entire MP3 library to FLAC will increase its size by 5-7×, take hours of CPU, and gain nothing audible. If you're doing this for archival or library standardization, fine — but be aware of the trade-off. If you have access to the original CDs or master files, rip those to FLAC instead.
Frequently Asked Questions
Will my listeners hear the difference between MP3 and FLAC of the same source?
No, because the FLAC was made from the MP3, so the audio data is identical. FLAC vs MP3 only matters when both come from a higher-quality source (a CD or master). Converting MP3 → FLAC and comparing them on playback will produce two files that sound exactly the same, modulo decoding precision (no audible difference).
How is FLAC different from ALAC (Apple Lossless)?
FLAC is open-source, free, and supported almost everywhere except Apple Music. ALAC is Apple's lossless format — same general idea, slightly different compression, but works in iTunes and on iPhones natively. If your library is for iPhones / Apple Music, prefer ALAC. For everything else, FLAC.
Is FLAC "better" than WAV?
They're audibly identical. WAV stores raw PCM with no compression; FLAC compresses that PCM with a lossless algorithm. A FLAC file is roughly 50-60% the size of the equivalent WAV. The trade-off: WAV has wider compatibility (every tool ever made supports it), FLAC saves space and supports tags. For pro audio workflows: WAV. For library archival: FLAC.
Can FLAC carry album art and detailed metadata?
Yes, fully. FLAC supports embedded album art, ID3-style tags (artist, title, album, year, track number, etc.), and even custom tags. WaveSieve doesn't write metadata during conversion, but Audacity, Mp3tag, and most music players can edit FLAC tags after the fact.