Audio Converter

Lossy and lossless, and why the order matters

A WAV file stores every sample exactly as it was captured. An MP3 does not: its encoder analyses the audio, works out which parts you are least likely to notice — quiet detail sitting underneath something loud, content near the limits of hearing — and throws them away, then compresses what remains. That is how a 40 MB file becomes 4 MB, and it is a one-way trip.

The practical consequence is that conversion direction matters enormously. Lossless to lossy is a normal, necessary step you do once at the end. Lossy to lossless is fine as a working step but recovers nothing. Lossy to lossy — MP3 in, MP3 out — is the one to avoid, because the second encoder makes its decisions about audio the first encoder already damaged, and the artefacts compound audibly.

So the rule for any workflow is simple: decode to lossless as early as you can, do all your editing there, and encode to a lossy format exactly once, at the very end, at the highest bitrate your target allows.

Sample rate, bit depth and channels

Sample rate sets how many times per second the waveform was measured, and it determines the highest frequency that can be represented — half the sample rate, the Nyquist limit. At 44.1 kHz that ceiling is 22.05 kHz, comfortably above human hearing, which is why the CD standard has survived four decades of arguments about it. Higher rates are useful during production, for the same reason 24-bit is: more room to work in, not more audible detail in the finished file.

Bit depth sets the resolution of each measurement and therefore the noise floor. 16-bit gives about 96 dB of dynamic range, which no domestic listening environment comes close to using. 24-bit gives around 144 dB, and its value is that you can record with generous headroom and still have the quiet passages sit far above the noise.

Channel layout is the one to change deliberately. Converting stereo to mono halves the file size and guarantees a consistent result on single-speaker devices, but it sums the two channels, and anything that was out of phase between them will partly cancel. Check a mono conversion by ear before you commit to it.

• Keep the source sample rate unless a platform demands a different one
• Deliver 16-bit; keep 24-bit for masters and works in progress
• 320 kbps MP3 for release, 192 kbps for previews, 128 kbps for speech
• Listen to a stereo-to-mono conversion before publishing it

Why converting in the browser is worth doing

Most online converters work by uploading your file to a server, processing it there and giving you a link. That means your audio — which might be unreleased, might be a client's, might be a private recording — sits on infrastructure you do not control, subject to a retention policy you have not read.

This converter does not upload anything. Your browser decodes the file with the same audio engine it uses to play music, the resampling and encoding run in JavaScript on your own machine, and the download comes from memory. It works offline once the page has loaded, and there is nothing to delete afterwards because nothing was ever sent.

Related tools

• Volume NormalizerNormalize music to a target loudness level.
• Audio Cutter & TrimmerTrim a track to the section you want, with clean fades.
• Audio AnalyzerInspect the technical and musical characteristics of any track.