Turn MP3 files into Opus
Your MP3 goes in and an Opus comes out. Opus is the usual choice for voice and video calls, WebRTC and game chat. Your file never leaves your computer.
Need the other direction? Convert Opus to MP3
How to convert MP3 to Opus
- 1 Drop your MP3 .mp3 file onto the page, or click to browse for it.
- 2 Set the quality, or leave the default, which keeps the file small without anything showing.
- 3 Convert. The work happens on your own machine, so how long it takes depends on your computer and the file.
- 4 Download the Opus, or add more files and do the whole set in one go.
Why convert MP3 to Opus
- The best sound for the size of any widely supported format.
- Latency as low as 5 ms, suitable for real time.
- Voice and video calls, WebRTC and game chat.
- MP3: no surround sound in practice, and no perfect-copy mode.
MP3 compared with Opus
How the two formats differ on the things that decide whether a conversion is worth making.
| Property | MP3 | Opus |
|---|---|---|
| File extension | .mp3 | .opus |
| Browser support | Every browser | All current browsers |
| Introduced | 1993 | 2012 |
| Developed by | Fraunhofer IIS | Xiph.Org and IETF |
Quality and what changes
Both formats are lossy, so this is a second generation of compression: the MP3 is decoded back to pixels that already carry its artefacts, and Opus then compresses that. The damage compounds rather than cancelling out, which is why repeated round trips visibly degrade an image. Encode at a higher quality than the source used, and convert once from the best copy you have rather than from an already converted file.
- One Opus limitation to keep in mind: detail is still thrown away, so it is not the format to archive in.
Questions about MP3 to Opus
Will converting MP3 to Opus lose quality?
A little. Both formats are lossy, so the file is decoded and compressed a second time and the two sets of artefacts add up. At a high quality setting the difference is hard to see, but avoid repeated round trips between lossy formats.
Is my MP3 file uploaded anywhere?
No. The whole thing runs inside the browser tab you already have open. Your MP3 is read straight from your own disk, converted on your machine and handed back as an Opus. Nothing is sent anywhere, nothing is stored and there is no account.
Is there a file size limit?
There is no server-side limit because no server sees the file. The real ceiling is your device memory, since the input and the output both have to fit in the tab. A few hundred megabytes is usually fine on a desktop machine and considerably less on a phone.
Can I convert several MP3 files at once?
Yes. Add as many as you like and they are processed one after another, then offered as separate Opus downloads or as a single ZIP. Speed depends on your own processor rather than on a queue.
Does the converter work offline?
Yes, after the page has loaded once. The engine is cached by the browser, so you can disconnect, reload and keep converting. That falls out of doing the work locally rather than being a separate mode you switch on.