Opus → MP3

Yes, and it is worth planning around. Both formats are lossy, so the MP3 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 MP3 from that instead avoids the double pass entirely. Opus scales from 6 kbps mono speech to 510 kbps stereo music in the same bitstream and switches modes automatically. MP3 is lossy: a psychoacoustic model discards frequencies the ear is unlikely to notice, typically at 128 to 320 kbps.

If Opus is lossy and MP3 is lossless (e.g. MP3 → WAV), the MP3 is no better than the Opus — you cannot recover information already discarded. If Opus is lossless and MP3 is lossy, the MP3 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 Opus stays 48 kHz in MP3. 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 MP3 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. Nothing beats MP3 for compatibility — car stereos, gym equipment, DAPs and twenty-year-old hardware all read it without question. MP3 is technically outclassed by AAC and Opus at every bitrate, cannot store more than two channels usefully, and always adds a small encoder delay.

Yes. Uploaded Opus files are processed on our own conversion servers, no person reviews them, and they are never shared. The upload and the converted MP3 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 MP3 as it is.