Audio Converter
Convert audio without uploading it
Convert MP3, WAV, OGG, FLAC, M4A and the audio inside a video to WAV, Opus or M4A — with trimming, resampling and normalisation.
Audio Converter
Runs in your browser · nothing uploadedUncompressed. Works in every browser, including those without WebCodecs.
01 — How to use Audio Converter
02 — Getting good results
03 — Questions
No. Decoding and encoding both happen in your browser using codecs it already ships with. No file is transmitted, which matters for recordings of meetings, interviews and anything else you would not hand to a stranger.
Because browsers can decode MP3 but not encode it, and adding an encoder would mean shipping a copyleft-licensed library. The alternatives are better anyway: WAV is lossless, Opus is more efficient than MP3, and M4A is as widely playable. MP3 files convert *in* perfectly well.
Opus and M4A need the WebCodecs API, available in Chrome, Edge and Safari 16.4 or later. WAV output needs no codec at all and works everywhere, so the tool is never entirely unavailable — it just says which formats this browser can produce.
Yes. Drop an MP4 or WebM and the audio track is decoded and converted like any other input. The video is discarded; nothing is re-encoded visually.
04 — More about Audio Converter
What converting audio actually involves
Compressed audio is not a recording so much as instructions for reconstructing one. Decoding turns those instructions back into a stream of samples — amplitude measurements taken tens of thousands of times a second — and encoding compresses that stream again using a different scheme. Everything between the two, such as resampling and trimming, operates on the raw samples, which is why order matters: trimming before resampling means the window you asked for is measured in the original timeline, while doing it the other way scales your times by the rate ratio and silently gives you a different section.
Lossy compression and generation loss
Lossy codecs work by discarding information the ear is unlikely to notice, guided by psychoacoustic models of masking — a loud sound hides quieter ones nearby in frequency and time. The discarded detail cannot be recovered, and each subsequent encode discards more, because the second encoder analyses a signal that is already the output of the first and makes its own, differently placed approximations. This is generation loss, and it is why an MP3 converted to Opus and back sounds worse than either conversion alone would suggest. Lossless formats such as WAV and FLAC avoid it entirely, at the cost of size.
Why this uses the browser’s own codecs
The usual way to do media conversion on the web is a WebAssembly build of ffmpeg, which works everywhere and can produce any format. It also weighs around thirty megabytes, downloaded by every visitor, and its core is licensed under the GPL, which imposes obligations on the site carrying it. WebCodecs takes the opposite approach: it exposes the encoders and decoders the browser already contains for playing media, so the download is nothing and the licensing question does not arise. It is also considerably faster, because those codecs are frequently hardware-accelerated. The trade is that the available formats are whatever the browser provides, and that support is not yet universal — which is why WAV, the one format needing no codec at all, is always available as a floor.
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where this came from.
Same shell, same shortcuts, same promise: nothing leaves your browser.