About MOV and Opus
MOV is Apple's QuickTime container, the default for iPhone recordings and screen captures on macOS. The audio track inside is usually AAC, which converts cleanly to anything here.
Opus is the newest codec here and the most efficient — it outperforms MP3, Vorbis, and AAC at low bitrates, which is why WhatsApp, Discord, and WebRTC all use it. Support is universal in browsers, patchier in older hardware.
Extracting audio from MOV re-encodes only the audio track — the video is discarded, so even long files finish quickly.
How the conversion works
This tool runs FFmpeg — the same engine behind most media software — compiled to WebAssembly, entirely in your browser. Your file is read locally, converted locally, and saved straight from memory; nothing is ever uploaded, which also means no queues and no server-side file size limits.
The converter itself is a one-time ~31 MB download on your first conversion, cached by the browser afterwards. Once it's loaded, everything works offline.