This extractor loads a WebAssembly build of FFmpeg only when you start. It maps the first audio stream and leaves out the picture, subtitles, chapters, attachments, and source metadata. MP3 uses LAME, M4A uses AAC, and WAV uses uncompressed 16-bit PCM.
MP3 and M4A are lossy formats, so 192 kbps is a sensible default for speech, meetings, and general listening. WAV avoids lossy encoding but creates a much larger file. Browser memory makes this tool best for short or moderate videos. Very long 4K files, damaged media, encrypted video, or unusual professional codecs may need a desktop editor.