Convert MP3 to Opus Online

"Online converter" normally means uploading your file to someone's server, waiting in a queue, and downloading the result. This page inverts that: it loads FFmpeg compiled to WebAssembly into your browser and does the work on your own machine. You keep the convenience of online — nothing to install, works on any OS — without the upload.

Expect a similar file size; the reason to convert is playback and workflow, not disk. That matters here, because transfer is where server-based converters spend most of their time. With no upload and no download of the result, what's left is just the conversion itself: usually a second or two.

MP3 files typically come from downloads, old rips, and just about every audio file that has ever been emailed — and MP3 is lossy and built for playback, so editing, production, and some apps and engines want a different format. MP3 already discarded data; Opus will discard a little more. Pick 192–320 kbps and it won't be audible in normal listening.

Because it's a web page rather than software, the same converter runs on Windows, macOS, Linux, ChromeOS, iPhone, and Android — with nothing to keep updated and none of the bundled adware that comes with downloadable free converters.

MP3 is the format of downloads. It plays where it was made, but MP3 is lossy and built for playback, so editing, production, and some apps and engines want a different format. Opus is the destination because it plays essentially everywhere — Discord recordings and every ordinary phone, browser, and player. Expect a similar file size; the reason to convert is playback and workflow, not disk. Both MP3 and Opus are lossy, so this pair stacks a second encode — at a generous bitrate it stays inaudible, but if a lossless original of the MP3 exists, encode the Opus from that instead.