About this tool
This decodes and re-encodes Opus audio to MP3 using ffmpeg.wasm — a full build of the real ffmpeg audio/video engine compiled to WebAssembly and loaded straight into your browser. Every file in the queue is processed with the same bitrate, sample rate, channel, trim, volume and fade settings above; nothing is ever sent to a server.
Why convert Opus to MP3 at all?
Opus is a modern, highly efficient codec — it's what Discord uses for voice messages, what WhatsApp uses for voice notes, what some Spotify and other streaming services use internally, and the default codec for WebRTC calls (video/voice chat in the browser). At a given file size it typically sounds better than MP3. But MP3 is still far more universally supported by old media players, car stereos, editing software, and devices that never added Opus support — converting trades away some of that efficiency in exchange for much broader compatibility.
My Opus file has a .ogg extension — is that a problem?
No — that's expected and this tool accepts it. Opus audio is very often packaged inside an Ogg container, which commonly gets saved with a .ogg extension instead of .opus (this is especially common with Discord voice messages and some WhatsApp exports). ffmpeg detects the actual audio codec from the file's contents, not its extension, so either extension works here.
Is my audio uploaded anywhere during conversion?
No. ffmpeg.wasm runs the entire decode/encode pipeline inside your browser via WebAssembly — your files never leave your device. The engine itself (roughly 25MB) does need to download the first time you use any converter tool on this site, then it's cached by your browser.