Audio to FLAC Converter

Convert Audio to FLAC Online

Turn almost any audio file into FLAC — the open, royalty-free lossless format maintained by the Xiph.Org Foundation. MP3, AAC, M4A, M4B, OGG, Opus, WMA, AC3, AMR, AIFF, AIF, AIFC, AU, OGA, WebA, VOC, and WAV all decode and re-encode to FLAC here. The honest part most converters skip: FLAC only preserves whatever quality the source has — it never adds quality back to a lossy file. The format-by-format outcomes are in the table below. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public.

How to Convert Audio to FLAC

1. Upload Your Audio File: Drag and drop your file onto the page or click "Add Files." You can queue several files and convert them in one batch with the same settings.
2. Set the Compression Level: The slider runs 1-12 and defaults to 12. Every level is lossless — a higher number spends more encoder CPU to shrink the file a little further, with zero difference at playback. The FLAC reference encoder only goes to 8; this tool exposes FFmpeg's extended 1-12 range.
3. Set Channel and Sample Rate (Optional): Leave Audio Channel and Audio Sample Rate on "Original" to pass the source through bit-for-bit — the right choice for an archive. Override only to downmix surround to stereo or match a target rate (44100 Hz for CD-style libraries, 48000 Hz for video work).
4. Convert and Download: Click "Convert" and save your FLAC. No sign-up, no watermark.

What FLAC Does to Your Source — Format by Format

The single most important thing to know before converting: FLAC is lossless, so it copies your audio exactly as-is. If the source was already lossy, FLAC faithfully preserves the lossy audio at a larger size — it cannot rebuild detail that the MP3/AAC encoder already threw away.

If your goal is a smaller file rather than a lossless one, stay in the lossy domain with the audio compressor instead. If you specifically need a single high-traffic pair, the dedicated WAV to FLAC and MP3 to FLAC pages do the same conversion.

Frequently Asked Questions

Does converting MP3 to FLAC improve the sound quality?

No, and nothing can. MP3, AAC, OGG, Opus, and WMA are lossy — encoding permanently discards audio data, and FLAC cannot rebuild what's gone. Converting a 128 kbps MP3 to FLAC produces a larger file that sounds exactly like the MP3. FLAC is worth it as a stable master for editing and archiving — every later edit, EQ pass, or re-encode on a lossy file compounds artifacts, whereas FLAC stays clean. To genuinely improve quality you have to go back to a lossless or higher-bitrate original; keep your masters.

Which sources actually shrink when converted to FLAC?

Only uncompressed ones. FLAC can losslessly pack raw PCM (WAV, AIFF, AU) down to roughly 40-55% of its original size, so converting WAV to FLAC is a real space win. It cannot shrink an already-compressed MP3 or AAC further — wrapping that lossy stream in FLAC adds container overhead, so the FLAC ends up larger than the lossy source while sounding identical. The table above lists the outcome per format.

What compression level should I pick?

For an archive, leave it at the default 12 — it squeezes out a few percent more than level 5 with no quality change and no slower playback. The trade-off is encode-time CPU only: higher levels run more prediction passes and take longer to write, but decode at the same speed at every level. The gains are asymptotic — most of the compressible redundancy is captured by level 5, and levels above 8 (which is the FLAC reference encoder's ceiling) typically save only 1-3% more per step.

Is FLAC really lossless, and how can I trust an old file is intact?

Yes — FLAC is mathematically lossless, so the decoded waveform is bit-identical to the PCM that went in. Every FLAC file also stores a 128-bit MD5 checksum of the unencoded audio in its STREAMINFO header, defined in RFC 9639, the format's formal specification published by the IETF in December 2024. A decoder can recompute that checksum years later and flag any corruption even when the bitstream itself still looks valid — something WAV and MP3 cannot do.

What input formats can I convert to FLAC here?

The converter accepts AAC, AC3, AIF, AIFC, AIFF, AMR, AU, DSS, M4A, M4B, MP3, OGA, OGG, Opus, VOC, WebA, WMA, WAV, and FLAC itself — 18 formats in all. Lossless sources become a smaller, verifiable FLAC; lossy sources become a faithful FLAC copy of the same audio. If you want an uncompressed file for a DAW instead, the audio to WAV converter decodes the same inputs to PCM.

Should I keep multichannel audio or downmix to stereo?

It depends on the target. Phones, laptops, and most headphones output stereo, so a stereo FLAC is more portable and roughly half the size. Keep the original layout when archiving 5.1 surround mixes or concert recordings for a home-theater setup. The Audio Channel control lets you force Mono, Stereo, or pass the source layout through unchanged. In our testing, a 3-minute 16-bit/44.1 kHz stereo WAV of about 30 MB encoded to a ~16 MB FLAC at the default level 12.

Will my files be kept or shared after I convert?

No. Your upload travels over an encrypted connection, is processed on our servers, and is deleted automatically a few hours after conversion. Files are never shared, never made public, and there's no sign-up, account, or watermark. If you'd rather convert FLAC back to a compressed format afterward, the FLAC to MP3 and FLAC to WAV pages handle the reverse.