Which format should I pick?

MP3 plays everywhere. M4A is often a lossless copy of the video's existing AAC track — the fastest and highest-quality option when it applies. WAV is uncompressed, for editing.

Does it work on any video?

Any video the engine can read — MP4, MOV, MKV, WebM, AVI and more. Audio-to-audio conversions (M4A → MP3, for instance) are handled by the Audio Converter.

Is my video uploaded?

No — the audio is extracted in your browser.

MP4 to MP3 — Free Audio Extractor