Audio converter

How to use the Audio Converter

1. Drop in audio files, video files, or both mixed together.
2. Pick the target in the Convert to menu; for MP3, M4A, AAC, OGG, Opus and WMA also pick a bitrate.
3. Under More settings, force mono or stereo or set 48, 44.1 or 22.05 kHz if the destination needs it.
4. Convert, then download the tracks one at a time or zipped together.

Choosing a target format

MP3 is the one every player, car stereo and website upload form understands. M4A (AAC) suits Apple devices and sounds slightly better than MP3 at low bitrates. Opus gives the smallest files for a given quality, FLAC keeps every sample for archiving, and WAV or AIFF hand editors plain 16-bit PCM.

Going from one lossy format to another costs a little detail each time, so convert from the best copy you own rather than from a file that has already been squeezed.

Copy instead of re-encode

When the audio inside the source already matches the chosen format and you leave channels and sample rate alone, the track is copied as it is. An MP4 clip with an AAC soundtrack saved as M4A finishes almost instantly and loses nothing; Opus out of a WebM saved as .opus works the same way.

Everything else goes through ffmpeg compiled to WebAssembly. Its engine, roughly 31 MB, comes from jsDelivr on first use and is cached by the browser, and the single-thread build is quick for audio because sound carries so little data compared with video.

Notes on Opus and WMA output

Opus output always runs at 48 kHz. Stereo tracks use ffmpeg’s own Opus encoder, which needs at least 96 kbps, so lower choices are raised to that; mono tracks use libopus at the bitrate you pick, which suits speech.

WMA output uses the Windows Media Audio 2 codec and tops out at 192 kbps. AIFF is written as 16-bit big-endian PCM and FLAC at compression level 5.

Questions