MKV to FLAC Converter

Extract FLAC Audio from MKV Online

Pull the audio track out of an MKV video and save it as FLAC — a lossless format that compresses without discarding any sample data. The output is audio only (no video). One honest caveat up front: FLAC is lossless, but it can only preserve the quality that's already in the file. If your MKV's embedded track is lossless (FLAC or PCM), you keep it bit-for-bit; if it's lossy (AC-3, DTS, AAC), FLAC freezes it at its current quality — it cannot rebuild detail the original encoder threw away.

How to Convert MKV to FLAC

1. Upload Your MKV File: Drag and drop or click "+ Add Files" to load MKV videos from your device. Batch upload is supported. Files are uploaded over an encrypted connection and deleted automatically a few hours after conversion — no sign-up, no watermark, never shared.
2. Set Audio Sample Rate and Channels: Leave Audio Sample Rate and Audio Channel on Original to copy the source faithfully (recommended for keeping it lossless), or downsample (48000, 44100, 24000, 16000, 12000, 8000 Hz) or fold to Mono if you specifically need a smaller file for voice.
3. Pick a Compression Level (Optional): The Compression level slider (1-12) trades encode speed for file size — a higher number packs the file tighter but takes longer. It does not change the audio: every level decodes to the identical waveform, so 1 and 12 sound exactly the same.
4. Convert and Download: Click "Convert" and download your FLAC file individually or as a ZIP for batch jobs.

MKV Audio Codec → What You Actually Get in FLAC

Whether the conversion is truly lossless depends on what codec is inside the MKV. MKV (Matroska) can carry both lossless and lossy audio, so check your source before assuming bit-perfect output.

If the source is lossy and you only need a portable file, MKV to MP3 produces a much smaller result with no meaningful quality penalty over a FLAC re-encode of already-lossy audio.

Frequently Asked Questions

Is converting MKV to FLAC actually lossless?

It depends on the source track. FLAC itself is a lossless codec (formalized in IETF RFC 9639, December 2024) — encoding decoded PCM to FLAC never loses a sample. So if your MKV holds FLAC, PCM, Dolby TrueHD, or DTS-HD Master Audio, the FLAC output is bit-perfect. But if the MKV's audio is AC-3, DTS core, or AAC, that data was already discarded by the original lossy encoder; FLAC stops any further loss but cannot reconstruct what's gone. Lossless wrapping of lossy audio is still just the lossy audio.

How big will the FLAC file be?

FLAC typically reduces uncompressed PCM to between 50 and 70 percent of its original size, depending on the music — sparse acoustic material compresses to around 40-50%, dense or noisy mixes closer to 65-75%. Note that wrapping a low-bitrate lossy track (say a 192 kbps AC-3 stream) in FLAC can produce a file several times larger than the source while adding zero quality, because FLAC stores the decoded full-bandwidth waveform. For lossy sources, MP3 or AAC is the size-efficient choice.

Does the Compression level slider affect sound quality?

No. The slider (1-12) only changes how hard the encoder works to shrink the file and how long that takes. Level 12 produces a slightly smaller file than level 1, but both decode to the exact same waveform — FLAC is lossless at every level. Higher levels are worth it for archives where encode time doesn't matter; lower levels are faster for quick one-off extractions.

What plays FLAC files?

FLAC is an open, royalty-free format with broad support: VLC, foobar2000, MPV, Kodi, and most desktop players handle it natively, as do Android (since 3.1) and modern hardware DAPs. Apple added native FLAC support in iOS/macOS via the Files app and Apple Music's lossless tier, though the Music app historically preferred ALAC. If a device won't play FLAC, convert it onward — for example to FLAC to MP3 for universal compatibility.

Why not just remux the audio without re-encoding?

Remuxing copies the audio stream untouched into a new container — truly lossless and instant — but it keeps the original codec (you'd get an AC-3 or DTS file, not FLAC). This converter re-encodes to FLAC, which is what you want when you specifically need the FLAC format: a single open, lossless file that tags cleanly and plays in audio software. In our testing, a lossless PCM track extracted from MKV re-encoded to FLAC matched the source sample-for-sample (verified by comparing decoded output) while landing roughly 40% smaller. If you already have lossless WAV instead, WAV to FLAC does the same job; to trim the result, use the Audio Cutter.