FLAC → Opus

Some, and it is permanent — this is the one direction where information is genuinely thrown away. FLAC holds every sample exactly; Opus discards what a psychoacoustic model predicts you will not hear. At 192 kbps and above that prediction is good enough to be transparent on most material and most equipment. Keep the FLAC as your master, because you cannot get back to it from the Opus. FLAC uses linear prediction plus Rice coding to reach roughly 50-60% of the original size while decoding back to bit-identical PCM. Opus scales from 6 kbps mono speech to 510 kbps stereo music in the same bitstream and switches modes automatically.

If FLAC is lossy and Opus is lossless (e.g. MP3 → WAV), the Opus is no better than the FLAC — you cannot recover information already discarded. If FLAC is lossless and Opus is lossy, the Opus codec recompresses; at 192 kbps the result is transparent for most content.

Several files in one job need a paid plan. Free use is one file per conversion, one conversion an hour. On a paid plan you can add several files to one job, then download each result on its own or all of them in one ZIP.

By default yes — 48 kHz FLAC stays 48 kHz in Opus. If you need to downsample for compatibility (96 kHz → 44.1 kHz for CD burning), the sample-rate option applies high-quality resampling in the same encode pass.

Not in this step. The converter has no loudness setting and leaves the level as it is. To even out the volume, run the finished Opus through a Normalize tool on this site.

MP3 plays almost everywhere. AAC plays on Apple devices, most Android phones and Sonos. FLAC plays on Sonos and Android but not on older iPods, and WAV plays on nearly everything but makes large files. There are no device presets on this page, so choose the target format your player supports. Opus is the best-sounding lossy codec at low bitrates by a clear margin, and it powers WhatsApp voice notes, Discord and WebRTC. Opus is almost never supported by standalone hardware — assume software playback only, and expect car stereos to ignore it.

Yes. Uploaded FLAC files are processed on our own conversion servers, no person reviews them, and they are never shared. The upload and the converted Opus are both deleted automatically about 24 hours after the conversion, which leaves time to download the result. See /privacy/ for the full policy.

It depends on the size and length of the file. Small documents and images are usually ready quickly. Long videos take the longest, because most video conversions re-encode every frame.

The converter does not change the level: it has no gain or normalize setting. If you hear a difference, your player or media library is probably applying ReplayGain or its own volume levelling on playback; switch that off to hear the Opus as it is.