OPUS (Opus Audio) and MP3 (MPEG-1 Audio Layer III) are built for different jobs. OPUS is typically used for voice notes, voip, while MP3 is best for music, podcasts, audiobooks. Converting lets you open, share or upload your files wherever MP3 is expected.
How to use the OPUS to MP3 converter
- Add your OPUS filesClick “Choose Files” or drag and drop them into the box. You can add many files at once — or paste a file with Ctrl+V.
- Choose MP3 and adjust settingsMP3 is selected automatically. Optionally open Settings to change bitrate, sample rate, channels or volume.
- Convert and downloadPress “Convert”. Your MP3 files appear instantly — download them one by one or all together as a ZIP.
OPUS vs MP3
OPUS Opus Audio
Opus is a modern codec that beats MP3 and AAC at low bitrates. WhatsApp voice notes, Discord and WebRTC calls use it, but many music players do not.
- Compression
- Lossy
- Features
- Very low latency
- Origin
- 2012, IETF
- Best for
- Voice notes, VoIP
MP3 MPEG-1 Audio Layer III
MP3 is the universal audio format. It shrinks music to around a tenth of CD size and plays on literally every phone, car stereo, speaker and app.
- Compression
- Lossy
- Features
- Stereo, ID3 tags
- Origin
- 1993, Fraunhofer IIS
- Best for
- Music, podcasts, audiobooks
Why use ConvertMathly?
Files are processed on your device and never uploaded. Close the tab and they are gone.
No account, no daily cap, no queue and no watermark — convert as much as you want.
The same engine used by professional video tools, running in your browser via WebAssembly.
Windows, Mac, Linux, Chromebook, iPhone and Android — any modern browser, nothing to install.
Frequently asked questions
How do I convert OPUS to MP3?
Add your OPUS files above, make sure MP3 is selected and press Convert. The MP3 files are ready to download a few seconds later — no installation or account required.
Why does the first conversion take a little longer?
The video engine (FFmpeg compiled to WebAssembly, about 30 MB) is downloaded once and then cached by your browser. After that, conversions start immediately — even offline.
Is there a file size limit?
There is no artificial limit. Because the conversion runs in your browser, the practical limit is your device memory — files up to around 1–2 GB work on most computers. Long videos take longer on phones.
Are my OPUS files uploaded to a server?
No. ConvertMathly converts files entirely inside your web browser using JavaScript and WebAssembly. Your files never leave your computer or phone, which makes it safe for private photos and documents.
Can I convert multiple OPUS files at once?
Yes — add as many files as you like. They are converted one after another and you can download everything in a single ZIP.