MP3 → Opus

Yes, and it is worth planning around. Both formats are lossy, so the Opus encoder is working from audio that has already been through one psychoacoustic pass, and its own decisions compound the first set. At 192 kbps or above the result is still transparent for most listening. If you have a lossless master anywhere, encoding the Opus from that instead avoids the double pass entirely. MP3 is lossy: a psychoacoustic model discards frequencies the ear is unlikely to notice, typically at 128 to 320 kbps. Opus scales from 6 kbps mono speech to 510 kbps stereo music in the same bitstream and switches modes automatically.

Often not. MP3 is decoded by essentially everything, including car head units and elderly players; Opus needs software that knows the codec, which standalone hardware frequently does not have. If the destination is a car stereo or a portable player, that is a strong argument for staying on MP3. Opus is almost never supported by standalone hardware — assume software playback only, and expect car stereos to ignore it.

If MP3 is lossy and Opus is lossless (e.g. MP3 → WAV), the Opus is no better than the MP3 — you cannot recover information already discarded. If MP3 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 MP3 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.

Yes. Uploaded MP3 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.