Step 1: Share your FLAC files using the button above or by drag and drop.
Step 2: Click the 'Transform' button to start the transformation.
Step 3: Grab your converted MKV files.
FLAC to MKV Transformation FAQ
How do I convert a FLAC file to MKV?
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Upload your FLAC file using the picker above and the converter detects the source type and runs the FLAC → MKV pipeline. The result downloads automatically when conversion completes; no account needed for one-off conversions. FLAC is the Free Lossless Audio Codec, an open format from 2001 that compresses without discarding a single sample. MKV is Matroska, an open container designed in 2002 with no licensing restrictions and no ceiling on what it can hold.
What will the picture be if I put FLAC audio into an MKV file?
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You choose it, because audio alone has no picture. The default is a static waveform render, and you can supply a still image instead — cover art, a title card, a photo — which is held for the whole duration. That is what makes the file uploadable to video-only platforms that will not accept a bare audio track. MKV is the archival container of choice because it stores unlimited audio tracks, soft subtitles, chapter markers and cover art in one file.
Is the FLAC audio re-encoded when it goes into the MKV?
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Only if it has to be. Where the MKV container accepts the source audio codec directly, the stream is copied in untouched and stays bit-identical. Where it does not, the audio is transcoded once to whatever MKV does accept, at a bitrate matched to the source so the second pass costs as little as possible. FLAC uses linear prediction plus Rice coding to reach roughly 50-60% of the original size while decoding back to bit-identical PCM. MKV is codec-agnostic: H.264, HEVC, VP9 and AV1 video sit happily beside AAC, FLAC, Opus, DTS or Dolby audio in the same file.
My FLAC is lossless — does putting it in an MKV throw that away?
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It usually does, because video containers expect a compressed audio track and most players will not accept raw PCM inside one. The audio is encoded once, at a high bitrate so the loss is inaudible, and the lossless FLAC stays untouched on your side. Keep it: it remains the master, and the MKV is a delivery copy. FLAC gives you WAV fidelity at half the size, with proper metadata tags and embedded artwork, which is why it dominates lossless music libraries.
How large will the MKV be compared with the FLAC?
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Barely larger, if you use the default still image. A single held frame compresses to almost nothing across the whole duration because every frame is identical to the last, so the file is dominated by the audio track. Choosing an animated waveform instead adds real video data and can double or triple the result.
Do the artist and album tags on my FLAC survive into the MKV?
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Partially. Title and artist map onto the video container’s own metadata fields, and embedded cover art is a natural fit for the still image the video displays. Everything else — track number, album, year, genre — has no equivalent slot in a video file and is dropped rather than approximated.
Will a surround mix in the FLAC stay surround inside the MKV?
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Yes — MKV carries multichannel audio properly, so a 5.1 mix stays 5.1 with the channel layout intact rather than being folded to stereo. That matters if the file is destined for a home cinema receiver rather than a phone, which will downmix at playback time anyway.
Is the FLAC to MKV converter free?
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Yes — basic FLAC → MKV conversion is free with no registration required. Premium adds higher per-file size limits, more parallel batch workers, longer retention, and removes ads.
How big a FLAC file can I convert to MKV?
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Free accounts: up to 100 MB per FLAC file. Premium: typically 1 GB per file depending on the source type. Very large files are split into chunks server-side when the MKV format allows.
Will conversion change the content of my FLAC?
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Conversion preserves all information that both FLAC and MKV can represent. Format-specific features the MKV cannot represent (e.g. vector data in raster output, formulas in plain-text output) are rasterized or stripped — the result page lists what changed.
Can I convert many FLAC files to MKV at once?
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Yes — drop multiple FLAC files into the upload zone and they are queued in parallel. Premium runs more parallel workers; on a 50-file batch this is the difference between minutes and seconds.
Does the FLAC to MKV converter work on phones and tablets?
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Yes — the UI is responsive and the conversion pipeline runs server-side, so mobile devices upload-then-download just like desktops. iOS and Android browser file pickers (camera roll, Files app) work end-to-end.
