Convert OPUS to FLAC Online
Convert Opus audio to FLAC container, free, in your browser.
.opus · up to 100 MB
What it's for
Opus to FLAC: zero additional degradation, maximum compatibility
Hi-Fi players
Hardware DACs, Astell&Kern, FiiO, and living-room audio systems that only accept FLAC or WAV.
No additional degradation
Unlike Opus→AAC or Opus→MP3, converting to FLAC adds no loss to already-compressed audio.
Metadata intact
Vorbis Comment tags from the Opus (artist, album, ReplayGain) are automatically transferred to the FLAC.
100% private
Your audio never leaves your device. Complete local conversion with FFmpeg.wasm, no servers.
How it works
Three steps, no hassle
Upload your Opus file
Drag or select your .opus file. Up to 200 MB, no signup required.
Repackaging to FLAC
FFmpeg.wasm decodes the Opus to PCM and re-encodes it to lossless FLAC in your browser.
Download your FLAC
Get your .flac ready for Hi-Fi players, Foobar2000, Roon, and long-term voice archives.
FAQ
Got questions?
No. This is the most important question and deserves a direct answer: converting Opus to FLAC does not restore or improve quality. Opus is a lossy codec: when the original audio was encoded to Opus, certain frequencies and details were permanently discarded by the psychoacoustic model. Decoding Opus to PCM and re-encoding to FLAC produces a lossless representation of the degraded PCM. The FLAC file will be larger than the Opus but will not have better quality. What is guaranteed is zero additional degradation: unlike transcoding to another lossy codec such as AAC or MP3, FLAC adds no further loss to audio already compressed with Opus.
There are legitimate use cases even though the no-quality-improvement principle holds: compatibility with Hi-Fi players and hardware DACs that only accept lossless formats (FLAC, WAV, AIFF) and reject Opus; long-term archiving of voice recordings with no risk of additional degradation from future transcodes; audio analysis software (Sonic Visualiser, Adobe Audition in some workflows) that requires lossless input; integration into Roon libraries, which though it supports Opus files, enables more complete analysis workflows with FLAC.
Significantly larger. A FLAC of a 1-minute voice file originally in Opus at 32 kbps will take approximately 5–6 MB (16-bit/48kHz FLAC of voice PCM), while the original Opus occupies about 240 kB. For musical audio at 160 kbps Opus over 5 minutes, the Opus weighs ~6 MB and the resulting FLAC ~50–60 MB. This size increase with no quality gain is the argument against using FLAC in all cases; it is only justified when the target system requires the format.
No. A FLAC of an original 24-bit/96 kHz recording has real high-resolution audio content. The FLAC resulting from decoding Opus contains the 48 kHz PCM reconstructed by the Opus decoder, which reflects the quality of the original Opus, not the source before Opus encoding. The difference is conceptually the same as between a photograph scanned from a print copy and the original photographic negative.
Yes. Both Opus and FLAC use the Vorbis Comment system for metadata. FFmpeg automatically transfers all fields: TITLE, ARTIST, ALBUM, DATE, TRACKNUMBER, GENRE, COMMENT, ALBUMARTIST, DISCNUMBER, and ReplayGain values (REPLAYGAIN_TRACK_GAIN, REPLAYGAIN_TRACK_PEAK) if present in the original Opus.
The libopus decoder produces 16-bit or 24-bit PCM depending on configuration. By default, FFmpeg.wasm produces 16-bit/48 kHz FLAC from Opus, which is sufficient for all information Opus can represent (Opus has effective resolution equivalent to 16-bit at its typical use bitrates). Producing 24-bit FLAC from Opus makes no sense, as the additional bits contain no real audio information.
Convert Opus to FLAC: archiving without additional degradation and Hi-Fi compatibility
FLAC (Free Lossless Audio Codec) was published by Josh Coalson in July 2001 as the first open-source lossless audio compression codec with mass adoption. The defining characteristic of FLAC is bit-perfect decoding: every sample of the decoded FLAC file is mathematically identical to the corresponding sample in the original uncompressed audio. This property makes it the de facto standard for high-fidelity audio distribution, archiving, and personal lossless music libraries. However, there is a frequent misunderstanding about what it means to convert a lossy file, such as Opus, to FLAC. Opus is a lossy codec standardized in RFC 6716 of September 2012: its psychoacoustic model discards audio components it considers inaudible to the human listener at a given bitrate. Once discarded, those components cannot be recovered, just as grain cannot be recovered from a JPEG-compressed photograph. Converting Opus to FLAC produces a FLAC that perfectly preserves the PCM reconstructed by the Opus decoder, without adding further loss, but that PCM is already the result of Opus's lossy process. The real utility of this conversion is not to improve quality but to eliminate the risk of additional degradation in future transcodes and to ensure compatibility with players and systems that only accept lossless formats.
The use cases where Opus to FLAC conversion has genuine technical justification are more common than they might seem. High-end portable audio players such as the Astell&Kern SP3000, FiiO M17, and Sony NW-WM1ZM2 have well-defined supported format lists: all accept FLAC, WAV, and AIFF, but Opus support varies by firmware. Home use hardware DACs (Chord Hugo, RME ADI-2 DAC, iFi Zen DAC) receive audio from software players like Foobar2000, Roon, or J. River Media Center, and although the software can decode Opus, some users prefer a fully lossless pipeline in their audio chain to simplify the signal. Roon, the high-fidelity music library management software, supports Opus in local files but has waveform analysis and volume normalization workflows that operate more consistently with FLAC. Long-term archiving of important voice recordings (journalistic interviews, field recordings, research audio archives) justifies converting to FLAC because although quality does not improve, the FLAC can be decoded without risk of additional degradation indefinitely, while keeping audio in Opus means any future necessary conversion would introduce a new generation of loss. The size difference is real and significant: an Opus of a 1-hour interview at 64 kbps occupies ~28 MB; the equivalent FLAC occupies ~500–600 MB. That size penalty is justified for archival-importance files.
Convertir.ai performs the Opus to FLAC conversion entirely in the browser with FFmpeg.wasm. The process decodes the Opus file with libopus to 48 kHz PCM (the native sample rate of Opus per RFC 6716), and re-encodes the resulting PCM with the libFLAC encoder at compression level 8 (maximum lossless compression, equivalent to flac --compression-level 8). The resulting FLAC is identical in audio content to the PCM produced by the Opus decoder: not one sample of difference. The FLAC encoder applies 12th-order linear prediction with Rice-Golomb entropy coding to minimize file size while maintaining perfect decoding. Vorbis Comment metadata from the original Opus file (TITLE, ARTIST, ALBUM, DATE, TRACKNUMBER, GENRE, COMMENT, ALBUMARTIST, DISCNUMBER) are automatically transferred to the VORBIS_COMMENT block of the resulting FLAC, including ReplayGain values if present. The output FLAC file is compatible with all FLAC-supporting players: Foobar2000, VLC, mpv, Audacious, Deadbeef, Roon, JRiver Media Center, MusicBee, and hardware players from Astell&Kern, FiiO, HiBy, Sony, and Pioneer. Processing occurs entirely locally: no audio is sent to external servers at any point. The service is free, with no file limit, no signup required, and no watermark.