Every time sound is squeezed into a smaller format, some detail is thrown away for good. Converting back up makes a bigger file, never a better one. Tell us what you have and what it's for; we'll show which rung to stop at and the tool that gets you there.
Digital audio measures the sound wave thousands of times a second and rounds each measurement to the nearest available step. Below, your browser does exactly that to a pure tone, then measures the rounding error it produced. Push the tone past half the sample rate to hear it fold back into a different note, or make it quiet at a low bit depth to watch it vanish. Every setting can be played and downloaded as a real WAV file.
Each source saves sound in its own format, and each has a usual next step. Every card links straight to the converter or tool that handles it.
Three tools that change the sound itself rather than its format. Drag the length to see what each would do with a file that long.
Loudness isn't the peak level. It's measured in LUFS, using the ITU-R BS.1770 method: the signal is filtered to roughly match how the ear weights frequencies, averaged in 400 ms blocks, and silent or very quiet blocks are gated out. This meter runs that algorithm in your browser on one of three generated clips or on your own file, which is decoded locally. It then shows what each platform would do to the level.
Play each row to hear the level that platform would use. Turning a track up is capped so the preview never clips. A real platform either limits the peaks or refuses the extra gain. Peaks are sample peaks: the true peak between samples can be up to about 0.5 dB higher.
Going down the ladder saves space and loses a little detail. Across it changes nothing you can hear. Going up never adds detail, but makes files editors and CD burners accept.
The last two columns are asked live, through canPlayType and MediaRecorder. “Transparent at” is the rough stereo bitrate where most listeners can't tell the result from the original in blind tests. It depends heavily on the encoder and the music.
The other toolboxes, with a typical job for each.