MP3 to FLAC Converter

How to Convert MP3 to FLAC Online

1. Upload Your MP3 File: Drag and drop or click "Add Files" to select your.mp3 file. Batch is supported, so you can queue several tracks or a whole album at once.
2. Pick a Compression Level: Default is 12 (smallest file, slowest encode). Lower values encode faster but produce a larger FLAC. Audio quality is identical at every level — only file size and encode time change.
3. Audio Channel and Sample Rate (Optional): Leave both at "Original" to preserve the source exactly. Switch Audio Channel to Mono to fold a stereo file down, or pick a different Audio Sample Rate (8000 Hz through 48000 Hz) only if a downstream tool requires it.
4. Trim (Optional) and Convert: Toggle Trim on and enter a Start Time and Duration in seconds or HH:MM:SS.sss to extract a segment. Click "Convert", then download the.flac file. No sign-up, no watermark.

Why Convert MP3 to FLAC?

FLAC (Free Lossless Audio Codec) is an open, royalty-free format developed by Xiph.Org that compresses audio with no quality loss — every sample decodes bit-identical to its input. Converting MP3 to FLAC does NOT restore audio data that MP3 encoding discarded; the FLAC file simply preserves the MP3's current quality without further degradation. With that caveat, the conversion is genuinely useful in several scenarios:

• Unify a mixed library — If most of your music is already FLAC but a handful of albums only exist as MP3 (Bandcamp purchases, old rips, podcast episodes), converting the MP3s to FLAC means your media server, music player, or DAP sees one consistent format and one consistent tagging scheme.
• Stop the re-encode bleed — Every time you re-encode a lossy file (MP3 to AAC, MP3 to MP3 at a different bitrate, MP3 to Opus), you lose a little more quality. Holding the audio in FLAC between edits — for example trimming an intro in an audio editor and exporting — means no further loss until you produce a final lossy copy.
• Better metadata — FLAC uses Vorbis comments, which are free-form key/value tags with no fixed length limit, embedded album art (PICTURE blocks), and ReplayGain. ID3v2 in MP3 works fine but has historical quirks (encoding ambiguity, frame ordering) that some library managers handle poorly.
• Audiophile and DAP compatibility — Many high-resolution audio players (HiBy, FiiO, Astell&Kern) and DACs prefer or require lossless input. Even if the source was MP3, those devices may handle a FLAC container more gracefully (gapless playback, embedded cuesheets).
• Archival and edit masters — For a podcast, voiceover, or sample, keeping the working file in FLAC means future trims or remasters don't compound MP3 artifacts. The MP3 stays as the distribution copy; the FLAC is the working master.
• CD authoring and DJ software — Tools like Mixxx, Rekordbox, and most CD-burning utilities accept FLAC natively and will resample/decode internally without re-applying lossy compression.

If you're hunting for the reverse direction (shipping a smaller file for streaming or upload), see FLAC to MP3. If you actually want uncompressed PCM, see MP3 to WAV.

MP3 vs FLAC — Format Comparison

Compression Level Quick Guide

Xconvert exposes a 1-12 slider that maps directly onto ffmpeg's FLAC encoder -compression_level parameter. The FLAC reference encoder itself defines levels 0-8; ffmpeg extends past 8 by enabling more exhaustive predictor and partition search. All levels are mathematically lossless — the decoded waveform is identical regardless of setting.

Frequently Asked Questions

Will converting MP3 to FLAC improve sound quality?

No. MP3 is a lossy format — the original encoder analyzed the audio and discarded sounds judged inaudible (psychoacoustic masking, frequency-band quantization). That data is gone and cannot be recovered. The resulting FLAC will sound identical to the source MP3 on every playback system. The benefit is forward-looking: subsequent edits, trims, or transcodes won't compound the loss.

Why is the FLAC file two to four times the size of my MP3?

FLAC stores every audio sample exactly. When it encodes your MP3, it first decodes the MP3 to PCM (the uncompressed waveform that, for CD-quality stereo, is roughly 10 MB/min), then losslessly compresses that PCM. Compared to a 128 kbps MP3 at ~1 MB/min, a typical FLAC of the same content lands around 3-5 MB/min — a 3-5x increase that reflects the gap between perceptual coding and true lossless coding.

Should I pick compression level 1, 5, 8, or 12?

For most users, the answer is: pick whatever finishes in a reasonable time, because the audio is bit-identical at every level. Empirical comparisons (see The Z-Issue's compression test) show level 8 produces files less than 1% smaller than level 5 while taking roughly 3x longer to encode. Levels 9-12 squeeze fractions of a percent more at significantly higher CPU cost. The FLAC reference default is 5; xconvert defaults to 12 for absolute minimum size.

Why is the file-size compression panel missing?

Bitrate-based controls (Quality Preset, Constant Bitrate, Variable Bitrate, target file size) only apply to lossy codecs that throw away data to hit a target rate. FLAC is lossless — there is no quality-vs-size tradeoff to expose, only the encode-speed-vs-size tradeoff that the Compression Level slider already covers. The panel is hidden to prevent users from setting parameters that the FLAC encoder would ignore.

Will the ID3 tags transfer to the FLAC file?

Title, artist, album, year, track number, genre, and embedded album art are mapped from MP3's ID3v2 frames to FLAC's Vorbis comments and PICTURE block during conversion. Less common ID3 fields (involvedpeople, mood, original release date, custom TXXX frames) may not map cleanly and sometimes have to be re-added in a tag editor like Mp3tag or Picard.

Can MP3 to FLAC be detected? Will audiophile software flag it as a "fake lossless"?

Yes — community tools like auCDtect and Spek analyze the frequency spectrum and detect the high-frequency rolloff MP3 encoders apply (typically truncating content above 16-19 kHz depending on bitrate). The resulting FLAC is technically lossless relative to the MP3 input but is not "lossless from the master." If you're sharing the file or uploading to a private tracker that bans transcodes, treat MP3-sourced FLACs as a no-go — they're considered deceptive.

Should I use FLAC, ALAC, WAV, or AAC instead?

FLAC and ALAC (Apple Lossless) are both lossless and roughly the same size; FLAC has wider third-party support, ALAC is preferred inside the Apple ecosystem (iTunes/Music app native support, Apple Music lossless tier uses ALAC). WAV is uncompressed — much larger files but trivially fast to seek and edit, useful for DAWs. AAC is lossy like MP3 but more efficient at the same bitrate; pick it only if you need a smaller file, not a lossless one.

Can I trim the audio during conversion?

Yes. Toggle the Trim control on and enter Start Time and Duration in either seconds (e.g., 30 for 30 seconds) or HH:MM:SS.sss format (e.g., 00:01:30.500). Only the requested segment is decoded from the MP3 and re-encoded into the FLAC. For more elaborate edits (multiple cuts, crossfades), use the dedicated Audio Cutter tool first, then convert.

Is there a file size limit?

Single-file uploads up to several hundred megabytes are fine; multi-hour podcasts or DJ mixes work too. Conversion runs on our servers — files aren't permanently stored, and there's no sign-up, watermark, or trial flag on the output.