Why Do This in Your Browser?
Audio format conversion is one of the most common one-off file operations — and yet it's the use case cloud converters built their entire businesses around. CloudConvert, OnlineAudioConverter, Zamzar; the playbook is upload, queue, download, walk away while paying for the privilege. The underlying conversion takes seconds.
FFmpeg.wasm handles every common audio format natively. The browser version stream-copies when the source and target codecs match (FLAC → FLAC container change), which is instant; transcodes when they don't (FLAC → MP3), at roughly 30–50x real-time on a recent laptop. A 60-minute audiobook converts in 2–3 minutes.
How It Works
Pick a target format and the tool figures out whether to stream-copy or transcode. Stream-copy preserves bit-exact audio (no quality loss whatsoever) and is the right choice for container changes (e.g., AAC inside MP4 → AAC inside M4A). Transcode is required when the codec changes (e.g., FLAC → MP3); the tool runs the source through the appropriate encoder with sensible default bitrates.
Format-specific defaults: MP3 (192kbps VBR, transparent for most listening), WAV (16-bit PCM, archival), AAC (192kbps VBR in M4A container), OGG (160kbps Vorbis), FLAC (lossless, smaller than WAV by ~50%), M4A (192kbps AAC). Custom bitrate/quality available for each.
Tip: If you also need to reduce file size, the Audio Compressor tool exposes finer bitrate controls. To extract audio from a video file first, use the Audio Extractor — it stream-copies when source codec is already AAC. For explicit sample-rate conversion separate from codec/container change (e.g., 44.1k → 48k for film delivery), the Audio Sample Rate Converter handles resampling with SoX-quality precision.
Common Use Cases
How We Compare
Honest read on free, paid, and self-hosted options for this kind of job:
See also: After converting an audio file, the Audio Waveform Generator produces a shareable waveform visualisation of the result.